Welding method and apparatus therefor

ABSTRACT

A welding process involves a fixture for holding a workpiece and a welder, or welding electrode. The fixture imposes ultrasonic vibration on the workpiece. The welder vibrates during vibration, and is operable at a first voltage for elding and a second voltage for peening. The peening may occur while the weldmetal is crystallizing. The welding process may be a process of welding two parts together, or of filling a groove or other feature, or of applying or restoring a surface, or of applying a hard facing or ceramic to a parent metal or object. The weldmetal may be the same, or substantially the same, as the parent metal, or it may be different. The different material may be a ceramic material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the priority of U.S. ProvisionalPatent Application Ser. No. 62/010,334, filed Jun. 10, 2014, thespecification and drawings thereof being incorporated by reference intheir entirety herein.

This application is a continuation of U.S. patent application Ser. No.14/569,307, filed Dec. 12, 2014, which claims the benefit under theParis Convention of the priority of Chinese Patent Application Nos. 20131068 1469.1 filed Dec. 16, 2013 and 2013 1068 1859.9 filed Dec. 16,2013, the specification and drawings thereof being incorporated hereinby reference.

FIELD OF THE INVENTION

This Application relates to methods and associated tools for welding.

BACKGROUND OF THE INVENTION

In a number of industries it may be helpful to be able to coat a metalsubstrate, or to join together by welding, or to make repairs by weldingprocesses of existing objects. The weld metal deposit may have certaindesired qualities with a coating of a similar or dissimilar material. Insome cases it may be desirable to coat a metal substrate with a ceramicsurface coating. Sometimes the coating is added for wear resistance, orto replace or re-surface a worn member.

In the electro-spark deposition (ESD) process, a consumable electrodematerial is brought into contact with a metallic base surface to betreated to deposit a coating, which may be a ceramic coating, on themetallic substrate. Electro-Spark Deposition (ESD). One such applicationmay pertain to welding electrodes for use in a production line. Weldingelectrodes are generally made of copper. The electrode may have asurface coating, such as a ceramic coating, that may be intended toincrease electrode life. However, the substrate material need not belimited to welding electrodes or to copper.

ESD is a low-stress surfacing-hardening process that causes littledistortion to the workpiece. ESD involves atomic-level metallurgicalbonding of a discharge electrode coating material to the base metal byelectro-spark discharge. ESD is a surface treatment process thatimproves the physical and mechanic properties of the surface of the basemetal. As a form of micro-arc welding technology, ESD introduces a largecurrent pulse during a capacitance discharge. A high temperature(5000˜25000 K) plasma arcing column melts or vaporizes a small part ofthe electrode rod coating material. The molten or vaporized electrodematerial is transferred to the surface of the base metal by this pulsedarcing micro welding. These traits permit ESD to be used in many surfacetreatment applications, including the surface coating of resistance spotwelding electrodes. Successful ESD examples of resistance spot weldingelectrode coatings includes the surface in-situ deposition of TiC, TiB2,and TiB2-TiC. Welding electrodes with TiC, TiB2 or TiC—TiB2 coatingshave been used in the spot welding of automobiles. ESD treated weldingelectrodes have made significant advances in industrial applications.coatings of vanadium-carbide, tungsten-carbide, titanium-diboride,zirconium-diboride, Titanium-carbide, Cr₃C₂, and so on, might be appliedto various tool steels or aluminum, or other metals. However, there aresome defects found in ESD coatings. For example, the grain in the heataffected zone (HAZ) near the coating layer may become coarse due to highthermal stresses arising during the ESD process (as shown in theFigures). Consequently, welding electrodes may not achieve the fullpotential life extension because of the flaws in the heat affect zone ofthe substrate matrix.

In the coating of welding caps using ESD technology, a TiC rod isconnected to the positive terminal of a capacitor, and then broughttoward the surface of a copper cap. The copper cap is connected to thenegative terminal of the capacitor. Arcing occurs when they are broughtclose together. This raises the temperature in the arcing column and amolten droplet is produced at the tip of the TiC rod. The molten dropletwill then be accelerated by the plasma jet and will strike the surfaceof the substrate forming a splash of TiC spot on the surface electrodematerial workpiece, and, if successful, the coating material will weldto the underlying substrate material. After many discharges, the surfacewill be covered in a layer of TiC coating. During the coating process,the molten droplets strike the substrate at a high velocity in thearcing column. As seen in FIGS. 18 a, 18 b and 18 c herein, splashingmay occur, resulting in cracks or delamination as observed in thecoating layer. These defects may tend to reduce the product life of thecaps to a great extent. Some researchers in university or industry havebeen trying to understand the cause of the coating defects and find waysto reduce them.

The surface area will be coated with a layer of the electrode materialwhen swept by the electrode. The electrode cap may be mounted to amoving device. The condition of the contact may be dependent on therelative motion of the rod of depositing electrode coating material andthe electrode cap to be coated.

Resistance spot welding is still the main technology used in theautomotive assembly, especially in body frame construction. The life ofwelding electrodes has become an important issue in the resistancewelding of galvanized steel and aluminum sheets. This in turn increasesthe consumption in automotive production and thus raises the productioncost. To solve this problem, researchers conducted many studies. Themost representative research result is the application of a protectivecoating layer (metallic or cermet) to the surface of welding electrodesthrough the electro-spark deposition process. This helps the weldingelectrodes to resist or delay alloy migration and plastic deformationduring welding, thus improving the usage life of resistance weldingelectrodes.

Electro-spark deposition (ESD) is a micro-arc pulse welding technologywhich transfers electrode material to a metallic substrate with the useof high frequency and short duration current pulses. The main advantageof electro-spark deposition is the ability to produce metallurgicalbonding between the coating material and the substrate base metal withlow heat transfer. Due to thermal shock when the spark discharges, ESDcoatings may tend to have flaws. FIG. 5 herein shows typical coatingdefeats (delaminations, porosity, cracks and uneven coating) of awelding electrode after the application of TiC coating using the ESDprocess.

Different types of processing technology have been tried by variousdomestic and foreign researchers to achieve grain refinement using thefriction stir welding processing. Ultrasonic grain refinementprocessing, as a secondary process technology, has been widely studiedand reported in areas such casting, welding, and surface materialtreatment. Kwanghyun Park was the first to study the ultrasonic assistedfriction stir spot welding equipment and processes. Ultrasonic assistedfriction stir welding process can produce welded joints with betterperformance than friction stir welding alone.

Friction stir processing technology is newly developed based on thefriction stir welding process for the surface coating modification ofcomposite material. Due to the unique thermal or mechanicalcharacteristics, or both, friction stir processing has been used01765842.1) in the preparation and modification of surface coatings.Zhou Xiaoping et al (Chinese invention patent CN201010570898.8, thepreparation and modification of Al2O3+TiB2+Al composite coating onaluminum surface by friction stir welding) has demonstrated that thedensity and micro-hardness of Al2O3+TiB2+Al composite coating producedby thermal spraying process can be improved by friction stir processing.

Similarly, Chinese invention patents (CN 201310050662.5) “A semi-solidultra fine grain/nano-crystalline plate processing method based onultrasound-assisted friction stir processing”, (CN 201310049003.X) “Anultrasound-assisted semi-solid friction stir processing method in acontrolled low temperature environment”, and (CN 201310049927.X) “arealization of surface UFG/nano material based on ultrasonic assistedsemi-solid friction stir processing method” have adoptedultrasound-assisted semi-solid friction stir processing technology,implemented with the use of a stirring pin for surface treatment. As aresult, a friction stir process may not be suitable for the modificationof surface coatings, such as those on resistance spot weldingelectrodes. In addition, the process is difficult, and power consumptionmay be high.

Resistance welding electrodes serve several purposes or functions: theconduction of welding current; application of closing pressure on themating parts to be welded, and heat dissipation. The temperature of thewelding electrode in contact with the workpiece is quite high, and thewelding electrode itself generates heat when welding current flows dueto its own internal resistance. The temperature on the top surface ofthe welding electrode may rise very quickly to a level that is onlymarginally lower than the weld nugget temperature.

In the view of the inventors herein, ultrasonic vibration may help toimprove welding structure and performance in the welding and castingindustries. Ultrasonic cavitation and acoustic streaming effects ofultrasonic vibration that may aid in refining grains in the heat affectszones of castings and weld pools. Chinese patent CN102019531A, whichpertains to a portable ultrasonic assisted electro-spark depositionintegrated repair and polish device and technology, suggests anultrasonic approach. However, the ultrasonic excitation is added tomodulation of the discharge electrode. This ultrasonic vibration appliesonly to the coating transfer of the deposition material. It appears tohave little effect on the coating layer on the base metal of theworkpiece.

SUMMARY OF INVENTION

The following summary is provided to introduce the reader to the moredetailed discussion to follow. The summary is not intended to limit ordefine the claims.

According to an aspect of the invention there is a vibrating hand-heldcoating material electrode holder. In another aspect of the inventionthere is a ventilated hand-held coating material electrode holder. In afurther aspect of the invention there is a vibrating hand-held coatingmaterial electrode holder that is internally ventilated.

In an aspect of the invention there is a welding apparatus. It has afixture to which to secure at least one workpiece; and a welding headpositioned to address a workpiece held in the fixture. The fixture has avibration source by which to transmit vibration to the workpiece. Thewelding head is one at least of (a) operable during welding to varyvoltage between a first magnitude and a second magnitude; and (b)operable during welding to vibrate independently of the fixture.

In a feature of that aspect of the invention, the apparatus includes atleast one ultrasonic vibration head operable to transmit ultrasonicvibration to the workpiece during welding. In another feature, theapparatus includes a power source operable to drive the welding head ina welding mode and in a peening mode. In still another feature, at leastone of the fixture and the welding head includes a motion transmittingdrive apart from a vibration drive, the motion transmitting drive isoperable globally to cause relative motion between the fixture and thewelding head. In a further feature, at least one of the fixture and thewelding head is programmable to move according to a pre-set course. Inanother feature, in use, the welding head is biased against theworkpiece. In still another feature, the vibration source of the fixturehas an engagement member for contacting the workpiece, and theengagement member is free from plastic deformation elements. In afurther feature, the welding apparatus is both (a) operable duringwelding to vary voltage between a first magnitude and a secondmagnitude; and (b) operable during welding to vibrate independently ofthe fixture.

In another aspect of the invention there is a method of welding aworkpiece. The method includes mounting a vibration source to transmit afirst vibration signal to the workpiece; opposing the workpiece with awelder; and operating the welder according to at least one of: (a)operating at a first voltage magnitude for a first time period; andoperating at a second voltage magnitude at a second time period; and (b)vibrating the welder according to a second vibration signal; andoperating the vibration source while operating the welder.

In a feature of that aspect of the invention, the method includesvibrating the welder to peen deposited weld metal during transmission ofthe first vibration signal. In another feature, the second voltagemagnitude is zero. In another feature, the method includes securing theworkpiece in a fixture. In a further feature, the method includes movingat least one of the fixture and the welding head along a pre-programmedpath while transmitting the first vibration signal to the workpiece. Inanother feature, the workpiece has more than one part, and the methodincludes welding at least two parts of the workpiece together.

In still another feature, the method includes operating the welder todeposit a material on the workpiece that is different from the parentmaterial of the workpiece. In anther feature, the method is a method ofsurface coating the workpiece. In still another feature, the firstvibration signal is an ultrasonic vibration signal the method includesboth (a) operating at a first voltage magnitude for a first time period;and operating at a second voltage magnitude at a second time period; and(b) vibrating the welder according to a second vibration signal; andoperating the vibration source while operating the welder.

In yet another feature, ultrasonic vibration is applied directly to theworkpiece during at least one of: (a) application of a welding rod tothe workpiece; (b) crystallization of welded material; and (c) peeningof welded material. In another feature it is applied during all of (a),(b), and (c). In another feature, ultrasonic vibration is applied to theworkpiece during at least two of: (a), (b), and (c). In a furtherfeature, the welding process is an ESD process and the welder uses awelding rod having a ceramic material composition that includes at leastone of (a) TiC; and (b) TiB₂.

In an aspect of the invention there is a coating material electrodeholder It has a seat in which to mount an electrode; a mechanical driveoperable to cause the electrode holder to move; and a power supplyconnection through which to supply electrical power to the electrode.The electrode holder has at least two modes of operation, the modes ofoperation including a first mode and a second mode. In the first modethe vibrator imposes mechanical motion upon the electrode seat andsupplies an ESD spark initiation voltage to the electrode seat. In thesecond mode the mechanical drive imposes mechanical motion upon theelectrode seat and supplies a voltage to the electrode seat that is oflesser magnitude than the ESD spark initiation voltage.

In a feature of that aspect of the invention the drive is a vibrator. Inanother feature, the holder is an hand held electrode holder. In afurther feature the second mode the voltage has zero magnitude. Inanother feature, the second mode the voltage is less than one half ofthe ESD spark initiation voltage. In a further feature, the driveoscillates, and is at least one of (a) amplitude adjustable; and (b)frequency adjustable.

In another aspect, there is an electrode holder for a coating materialelectrode. The holder has an electrically insulated handle by which anoperator may grasp the electrode holder; an electrode seat mounted tothe handle, the electrode seat defining a seat for an electrode rod; apower source in electrically conductive connection with the electrodeseat, whereby an electrode rod received in the electrode seat mayreceive electrical current from the power source; and a vibration sourcemounted to the handle; and a power supply controller. The power supplycontroller is operable to supply power to the electrode seat in at leasta first mode and a second mode. In the first mode the power supply isset to supply power at a first voltage, the first voltage being an ESDinitiation voltage. In the second mode the power supply is set to supplypower at a second voltage, the second voltage having a magnitude lessthan the ESD initiation voltage.

In a feature of that aspect of the invention, the vibration source isfrequency adjustable. In another feature, the vibration source has anoutput frequency in the range of 100 Hz to 500 Hz. In another feature,the second voltage is less than half the ESD initiation voltage. In afurther feature, the vibration source includes an exciter and aresilient transmitter, the electrode seat being mounted to the resilienttransmitter. In still another feature, the transmitter is adjustablytunable in vibration frequency. In yet another feature, the electrodeseat has an axial direction associated with a long axis of electroderods mounted therein, and the vibration source, in operation, oscillatesthe handle with a component of force in the axial direction. In stillanother feature, the electrode seat has an axial direction; the exciteroscillates in operation; and oscillation of the exciter includes acomponent of force in the axial direction. In another feature, theexciter includes a rotating eccentric. In still another feature, theresilient transmitter includes a spring mounted between the exciter andthe electrode seat. In yet another feature, the electrode seat isadjustably orientable relative to the handle. In still yet anotherfeature, the electrode holder includes at least one electrical brushmounted between the power source and the electrode seat, whereby theelectrode seat remains in electrically conducting relationship to thepower source notwithstanding re-orientation of the electrode seat.

In another aspect there is a method of surface coating treatment of acoated welding electrode, the coating material having a meltingtemperature. The method includes establishing a coating depositionportion on at least a first region of the welding electrode at anelevated temperature less than the melting temperature of the coatingmaterial; and plastically deforming that coating deposition portion atthat elevated temperature.

In a feature of that aspect, the method includes beating the coatingdeposition portion. In another feature, the method includes melting aportion of a coating material electrode onto the welding electrode toestablish the coating deposition portion; and using the coating materialelectrode subsequently to strike the coating deposition portion at theelevated temperature thereby plastically to deform it. In anotherfeature, the method includes applying a first voltage to establish thecoating deposition portion, the first voltage being a melting voltage;and applying a second voltage, the second voltage being a non-meltingvoltage when plastically deforming the coating deposition portion. Inanother feature, the second voltage has a magnitude that is one of: (a)less than the first voltage; and (b) substantially zero. In a stillfurther feature, the method includes establishing vibratory relativemotion between the coating material electrode and the welding electrodeworkpiece.

In another aspect, there is a method of depositing a coating on awelding electrode workpiece. The method includes establishing a coatingmaterial electrode in an electrode holder proximate to a workpiece;establishing a first voltage differential between the coating materialelectrode and the electrode workpiece, the first voltage differentialbeing at least as great as an ESD initiation voltage; striking an arcbetween the coating material electrode and the welding electrodeworkpiece whereby to cause material of the coating material electrode tobe deposited on the electrode workpiece; breaking contact between thecoating material electrode and the electrode workpiece; and striking theelectrode workpiece again while the coating material electrode is at asecond voltage differential, the second voltage differential being oflesser magnitude than the ESD initiation voltage.

In a feature of that aspect, the welding electrode workpiece is mountedto a drive, the drive being operable to move the welding electrodeworkpiece in at least one degree of freedom of motion while the coatingmaterial electrode is held in the electrode holder; and while theelectrode rod is biased against the workpiece, vibrating the electrodeholder, whereby coating material from the coating material electrode isdeposited on the workpiece. In another feature, the second voltagedifferential has substantially zero magnitude. In a further feature, thesecond voltage differential is less than one half of the ESD initiationvoltage. In another feature, the method includes establishing vibratorymotion between the coating material electrode and the electrodeworkpiece. In a still further feature, the method includes establishingthe vibratory motion in a frequency range between 100 Hz and 500 Hz. Instill another feature, the method includes adjusting the voltagedifferential between contact periods of the coating material electrodeand the electrode workpiece. In yet another feature, the method includesplastically deforming deposited coating material from the coatingmaterial electrode as that deposited material cools on the electrodeworkpiece. In a further feature, the ESD initiation voltage is in therange of 25-50 V. In still another feature, the second voltage is in therange of 5 to 30 V.

In a further feature of any of the methods herein, the electrode rod isa ceramic composition. In a further feature that ceramic composition istitanium carbide or titanium diboride. In another feature the rod is anickel rod.

In a further aspect of the invention there is the method of using any ofthe apparatus having any combination of the aspects and featuresdescribed herein, that method including the steps of mounting theelectrode in the holder, or causing the holder to vibrate, and ofplacing the electrode and the work piece in contact while charged withopposite electrical polarities.

In an aspect of the invention there is a surface modification apparatusand method for treating electro-spark deposition coating layers. It mayinclude a processing method for a surface coating in which there is useof a flat or curved shaped head applying pressurized, or force biasedrotating friction to the surface coating on a workpiece. Ultrasonicvibration is simultaneously applied to the workpiece or the rotatinghead. In a feature of that aspect of the invention the shape of thefriction spinning head or probe is flat or curved surface, without aprojection spinning pin or needle.

In this aspect, it may be that the coating material would not be removedfrom the base material of the workpiece. It may be that no base materialof the substrate is disturbed in the process. This may help to maintainthe coating material composition during the process. With the additionof ultrasonic vibration to the surface coating during the process,coating defects (delaminations, porosity, cracks and uneven coating) maybe reduced or eliminated and high binding strength to the base materialmay be achieved. In addition, the physical and mechanical properties ofthe coating may also be improved.

In a feature of that aspect of the invention, the force-biased rotatingfriction head and the workpiece spin in opposite directions. The surfacecoating may undergo a continuous treatment process. The composition ofthe surface coating may remain unchanged while coating defects areeliminated giving better coating performance as a result.

In another aspect of the invention there is an apparatus for the surfacemodification of surface coating on workpieces. It includes a work tablefor the clamping of the workpieces. It has an ultrasonic, force-biasedrotating friction device and an ultrasonic power source. The ultrasonicrotating friction device has a force-biased rotating friction module andan ultrasonic transducer. The ultrasonic transducer is electricallyconnected to the ultrasonic power source. The shape of the rotatingfriction probe may be either flat or curved. The friction probe may befree of any projection pin on the flat or curved surface thereof. Thesurface may be planar.

In various features of that aspect of the invention, the apparatus mayinclude one or more of the following: a rotating electrode holderworkstation having an equipment frame, an electric motor, a transmissionbelt, pulley, supporting bearings, a transmission shaft, a clampingchuck and a dual guiding rails; an integrated ultrasonic transducer withrotating friction head apparatus comprising: a pair of sliders, upperand lower panels, screw shaft, positive and negative inputs of theultrasonic power, a sliding conductor, bearings, a belt pulley, adriving belt, an electric motor, an ultrasonic transducer, a transducerhorn, a rotating friction head and the housing; an ultrasonic powersource having ultrasonic positive output terminal, an ultrasonic powercontrol knob, the ultrasonic negative output terminal, and a powerswitch.

Integration of the workstation, pressurized rotating friction module andthe ultrasonic power source: The equipment frame is fixed to theworkstation, the electric motor drives the transmission shaft throughthe coupling of the driving belt and pulley; the clamping chuck for workpieces is mounted to the transmission shaft; The integrated rotatingfriction assembly is fitted to the workstation through the fitting ofthe sliders to achieve free repeating movements, this allows rotatingfriction application to the surface coating of workpiece on theworkstation assembly; the lower panel of the rotating friction assemblyis attached to the upper panel through the coupling of the screw shaft,this allows the rotating friction assembly to move in a verticaldirection and thus to achieve the application of pressure during theprocess by adjusting the screw shaft; the ultrasonic input +ve and −veterminals are connected to the corresponding terminals of the ultrasonicpower source; the sliding conductor is connected to the ultrasonictransducer with the use of electrical wires; the transducer horn ismounted to the ultrasonic transducer; the rotating friction head isdriven to rotate through the driving of the electric motor, drivingbelt, belt pulley and the support bearing; this setup achieves theapplication of the pressurized rotating friction to workpiece on theworkstation; the rotating friction assembly is then enclosed in thehousing.

On the workstation, the clamping chuck for mounting the workpiece isdriven to rotate by the electric motor through the transmission of thedriving belt and pulley. With the fitting of the 2 sliders on the lowerpanel and the 2 guiding rails on the workstation, the integratedultrasonic rotating friction assembly can be used to process theworkpiece repeatedly.

With the integrated ultrasonic rotating friction assembly attached tothe upper panel, the upper panel is attached to the lower panel throughthe screw shaft. Not only does the screw shaft move the upper panel in avertical direction, it also allows certain pressure to be applied to theworkpiece. The ultrasonic rotating friction assembly is driven by themotor through the transmission of the pulley, belt and bearings. Throughthe adjustment to the screw shaft, the pin-less friction head can bemoved to make friction contract with the workpiece. Furthermore, withthe application of pressure and the ultrasonic vibration simultaneously,it is made possible to modify surface coatings on workpiece usingultrasonic pressurized rotating friction processing.

In an aspect of the invention there is a process of surface treatment ofan ESD coating. The process includes biasing a friction head assemblyagainst a workpiece to which an ESD coating is applied; moving theworkpiece relative to the friction head while in contact therewith; andsubjecting the coating to ultrasonic vibration while the friction headis in contact therewith.

In a feature of that aspect of the invention, the process includesrotating the workpiece while the friction head is in contact therewith.In another feature, the process includes rotating said friction headassembly while it is in contact with the workpiece. In a further,additional feature, the process includes rotating the workpiece whilethe friction head is in contact therewith. In another feature, thecoating is a TiC coating. In another feature, the process includesdepositing the ESD coating. In still other features, the process mayinclude at least one of: (a) an ultrasonic frequency of about 50 kHz;(b) a biasing force of about 200N; and (c) a rotational speed of therotating friction head of about 1400 rpm.

In another aspect of the invention, there is an apparatus for theprocessing of surface coating modifications of an ESD coating on aworkpiece surface. The apparatus has a work station for the mounting androtation of the workpiece; a friction assembly, operable, in use, to bebiased against the workpiece; and an ultrasonic transducer mounted totransmit ultrasonic vibration to the workpiece while the workpiece is incontact with the rotating friction assembly.

In a feature of that aspect of the invention, the apparatus has anultrasonic power source; and the ultrasonic transducer is connected tothe ultrasonic power source. In another feature, the friction head has ashape that is one of (a) flat; and (b) curved. In still another feature,the friction assembly is also mounted for rotation. In still yet anotheradditional feature, the apparatus is such that at least one of (a) theultrasonic transducer operates at about 50 kHz; (b) in use, the biasingforce is about 200N; and (c) the friction head is mounted for rotationat about 1400 rpm.

In another aspect of the invention there is a surface coating processfor use in applying an ESD coating to a workpiece. The process includesapplying a surface coating to a workpiece using electro-sparkdeposition; and applying ultrasonic vibration to the workpiece.

In a feature of that aspect of the invention, the ultrasonic vibrationis applied to the workpiece during the electro-spark deposition of thecoating. In another feature, the ultrasonic vibration is applied to theworkpiece during crystallization of the coating. In still anotherfeature, the ultrasonic vibration is applied to the workpiece during theelectro-spark deposition of the coating and during crystallization ofthe coating. In a further feature, the ESD coating is deposited on theworkpiece by an applicator. The applicator is a vibrating applicator.The applicator vibrates during deposition of the coating independentlyof the ultrasonic vibration. In still another feature, the workpiece isheld in a rotating tool holder, and the workpiece is driven to rotateduring the process. In a further additional feature, at least one of (a)the ultrasonic vibration is applied to the workpiece during theelectro-spark deposition of the coating; and (b) the ultrasonicvibration is applied to the workpiece during crystallization of thecoating. In a still further feature, the ESD coating is deposited on theworkpiece by an applicator. The applicator is a vibrating applicator,and the applicator vibrates during deposition of the coating in additionto the ultrasonic vibration.

In another feature, the ESD coating is deposited on the workpiece by anapplicator. The applicator is a vibrating applicator, and the applicatorvibrates during deposition of the coating in addition to the ultrasonicvibration. In an additional feature, the process includes applying theESD coating to a resistance spot welding electrode as the workpiece. Instill another feature, the process includes depositing a coating thatincludes at least one of (a) TiC and (b) TiB₂, on the workpiece. In yetanother feature, the process includes applying the coating to a metalmatrix that includes copper. In a still further feature, the processincludes applying the ESD coating to a resistance spot welding electrodeas the workpiece, that spot welding electrode having a metal matrix thatincludes copper; and depositing a coating that includes at least one of(a) TiC and (b) TiB₂, on the workpiece.

In another aspect of the invention there is an apparatus forelectro-spark deposition of a surface coating on a workpiece. Theapparatus has a tool holder to which the workpiece is mounted; a coatingapplicator; and an ultrasonic vibration source mounted to act on thetool holder, and thereby directly to apply ultrasonic vibration to theworkpiece.

In a feature of that aspect of the invention, the ultrasonic vibrationsource is operably connected to apply ultrasonic vibration to the toolholder at least one of (a) during the electro-spark deposition of thecoating; and (b) during crystallization of the coating. In anotherfeature, the coating applicator is a vibrating coating applicator. In afurther feature, the tool holder is a rotating tool holder. In stillanother feature, the tool holder is a rotating tool holder; and theultrasonic vibration source is operably connected to apply ultrasonicvibration to the tool holder at least one of: (a) during theelectro-spark deposition of the coating; and (b) during crystallizationof the coating. In a further additional feature, the coating applicatoris a vibrating coating applicator. In a still further feature, theworkpiece is a resistance spot welding electrode. In another feature,the apparatus has a vibrating applicator, an ESD power supply, anultrasonic transducer assembly, a work station having a rotating driveand an ultrasonic generator; the ultrasonic generator being connected todrive the ultrasonic transducer; the ultrasonic transducer assembly andthe rotating drive work station being assembled as a single integratedunit; and the workpiece being mountable in a tool holder seat vibratedby the ultrasonic transducer.

In still another feature, the apparatus includes: an ESD power supplyhaving a positive power terminal and a negative power terminal; avibrating applicator having a resilient conductor spring, a dischargeelectrode mounting, a discharge electrode, a driven eccentric, a handle,an insulated support, a flexible drive shaft, and a low-power applicatormotor; an integrated transducer assembly on which to mount a workpieceto be coated; a work-station negative terminal, an integrated transducernegative terminal, an integrated transducer positive terminal, anintegrated transducer body, a transducer horn, an ultrasonic transducer,a flat pulley, bearing, and tool holder; a work-station drive assemblyhaving a work bench drive motor, a drive belt; an ultrasonic generatorhaving an ultrasonic power output negative terminal, and an ultrasonicpower output positive terminal. The ESD power positive terminal isconnected to the conductor spring. The ESD power negative terminal isconnected to the work-station negative terminal. The discharge electrodeis mounted to the conductor spring. The applicator is connected to thelow-power motor through the flexible shaft. The eccentric wheel isdriven in rotation by the driving of the low-power motor through theflexible shaft to drive vibrating deposition. The ultrasonic poweroutput negative terminal is connected to the integrated transducernegative terminal. The ultrasonic power output positive terminal isconnected to the integrated transducer negative terminal. The integratedultrasonic transducer assembly is driven in rotation by the drive motorthrough the flat pulley and drive belt. The ultrasonic transducer isconnected to the integrated transducer negative terminal and theintegrated transducer positive terminal, respectively. The transducerhorn and ultrasonic transducer are combined to form a shaft of therotary work station; the tool holder being mounted to the rotary workstation; whereby the workpiece is mounted to the work-station forrotating ultrasonic-assisted electro-spark deposition.

There are many combinations and permutations of aspects and features. Itwill be understood that any of the features may be combined, asappropriate, with any of the aspects enumerated herein.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

The foregoing aspects and features of the invention may be explained andunderstood with the aid of the accompanying illustrations, in which:

FIG. 1 is a general arrangement perspective view of an electrode handleapparatus according to an aspect of the invention herein;

FIG. 2 is a first side view of the electrode handle apparatus of FIG. 1;

FIG. 3 is a top view of the electrode handle of FIG. 1;

FIG. 4 is a side view of the electrode handle of FIG. 2 with thenear-side handle haft removed to expose interior features;

FIG. 5 is a longitudinal cross-sectional view of the electrode handle ofFIG. 2;

FIG. 6 is an end view of the electrode handle apparatus of FIG. 1;

FIG. 7 is a side view of an alternate embodiment of electrode handle tothat of FIG. 1;

FIG. 8 shows the electrode handle of FIG. 7 with the near side of thehousing removed; and

FIG. 9 shows a cross-section of the electrode handle of FIG. 7 along itslongitudinal central plane.

FIG. 10 shows a general arrangement perspective view of an alternateelectrode handle apparatus to that of FIG. 1;

FIG. 11 is a first side view of the electrode handle apparatus of FIG.10;

FIG. 12 is a bottom view of the electrode handle of FIG. 10;

FIG. 13 is an opposite side view to that of FIG. 11; and

FIG. 14 is a head end view of the apparatus of FIG. 10.

FIG. 15 a shows a first side view of an alternate apparatus to that ofFIG. 1;

FIG. 15 b show a second, opposite side view of the apparatus of FIG. 15a with the foreground housing removed to reveal interior detail;

FIG. 16 is a schematic of a power source for the handle of FIG. 1, 10;or 15 a;

FIG. 17 a is a schematic representation of alternating coating andpeening stages as might be applied with the power source of FIG. 16;

FIG. 17 b is a time schedule for deposition and peening switch-“On” and“Off” conditions for of the power source of FIG. 16;

FIG. 17 c is a Time v. Voltage representation applied to and through theelectrode rod of the apparatus by the switching of FIG. 17 a;

FIG. 17 d is an alternate plot of Switching v. Time for an alternateembodiment of operation of the power source of FIG. 16;

FIG. 18 a is a much enlarged photograph of a “splash” of ESD coatingmaterial;

FIG. 18 b shows an enlarged view of as-coated ESD workpiece surface; and

FIG. 18 c is an enlarged cross-sectional view of an ESD coating sampleon a workpiece;

FIG. 18 d is a photograph of defects in an ESD coating in a surfaceview;

FIG. 18 e is a photograph of defects in an ESD coating in anothersurface view;

FIG. 18 f is a photograph of typical defects in an ESD coating in across sectional view;

FIG. 18 g is a photographic view showing a comparison in cross-sectionof ESD coating SEM views of effects of the ultrasonic pressurizedrotating friction processing, FIG. 18 g being a before the process view;

FIG. 18 h is a photographic view showing a comparison in cross-sectionof ESD coating SEM views of effects of the ultrasonic pressurizedrotating friction processing, FIG. 18 h being an after the process view.

FIG. 19 is a cross-sectional view of a welding arrangement according toan aspect of the invention herein;

FIG. 20 is a side view of a welding arrangement of an aspect of theinvention;

FIG. 21 shows a conceptual relationship of elements according to anembodiment of the invention;

FIG. 22 shows a schematic view of a workstation for the clamping androtation of a workpiece such as may be coated according to theembodiment of FIG. 21;

FIG. 23 shows a general layout of structural and operational elements ofan integrated ultrasonic rotating friction assembly according to theembodiment of FIG. 21;

FIG. 24 shows an ultrasonic power source for the embodiment of FIG. 21;

FIG. 25 is a conceptual illustration of an embodiment of apparatusaccording to an aspect of the invention herein;

FIG. 26 is a basic illustration of a workbench of the apparatus of FIG.25;

FIG. 27 a shows a metallurgical comparison chart of coatings ofdifferent technology, FIG. 27 a being a coating that is notultrasonic-assisted;

FIG. 27 b shows a metallurgical comparison chart of coatings ofdifferent technology, FIG. 27 b being a coating that is notultrasonic-assisted;

FIG. 28 is a micro-hardness comparison of different coating technology;and

FIG. 29 is a metallurgical chart of a coating under patent CN102019531A.

DETAILED DESCRIPTION

The description that follows, and the embodiments described therein, areprovided by way of illustration of an example, or examples, ofparticular embodiments of the principles of aspects and features of theinvention. These examples are provided for the purposes of explanation,and not of limitation, of those principles and of the invention. In thedescription, like parts are marked throughout the specification and thedrawings with the same respective reference numerals. The drawings maybe taken as being to scale, or generally proportionate, unless indicatedotherwise. The photographic views may be taken as being to scale, orgenerally proportionate, unless indicated otherwise.

The scope of the invention herein is defined by the claims. Though theclaims are supported by the description, they are not limited to anyparticular example or embodiment, and any claim may encompass processesor apparatus other than the specific examples described below. Otherthan as indicated in the claims themselves, the claims may not belimited to apparatus or processes having all of the features of any oneapparatus or process described below, or to features common to multipleor all of the apparatus described below.

The terminology used in this specification is thought to be consistentwith the customary and ordinary meanings of those terms as they would beunderstood by a person of ordinary skill in the art in North America.Following from the decision of the Court of Appeal for the FederalCircuit in Phillips v. AWH Corp., the Applicant expressly excludes allinterpretations that are inconsistent with this specification, and, inparticular, expressly excludes any interpretation of the claims or thelanguage used in this specification such as may be made in the USPTO, orin any other Patent Office, other than those interpretations for whichexpress support can be demonstrated in this specification or inobjective evidence of record in accordance with In re Lee, (for example,earlier publications by persons not employed by the USPTO or any otherPatent Office), demonstrating how the terms are used and understood bypersons of ordinary skill in the art, or by way of expert evidence of aperson or persons of experience in the art.

Reference is made herein to welding electrode tips and caps, which areintended to provide a generic example of a work piece that is movablewith respect to at least one degree-of-freedom of motion while beingcoated. Other objects could also be coated. In respect of each tip orcap that is spinning on a mandrel, a polar-cylindrical co-ordinatesystem may be defined, in which the axial, or z-direction defines theaxis about which the cap or electrode tip is formed, or has a surface,on a body of revolution, the term radial refers to a distance away fromthe z-axis, and circumferential refers to an angular direction about thez-axis. For generality, the workpiece may be other than a welding cap,and may be mounted for one or two degrees-of-freedom of motion intranslation in, for example, an x-y plane in a Cartesian co-ordinatesystem or frame of reference. That motion may be reciprocating or cyclicmotion, and may include both rotational and translational components.

By way of general overview, an electrode handle apparatus, or simply ahandle, is shown in FIG. 1 as 20. Apparatus 20 has an electrode holder,indicated generally as 22, in which an electrode 24 is mounted.Electrode 24 has a cylindrical shape, and is relatively long and thin.Electrode 24 may be a semi-conducting material, such as titaniumcarbide, titanium di-boride, or such other material as may be. Theoutwardly extending tip of electrode 24 is seen positioned toward anobject apparatus 26, which includes a mandrel 28 upon which is mounted aworkpiece to be coated, such as may be a welding electrode cap 30. Bythe nature of the coating process, electrode rod 24 is consumable andreplaceable. The mandrel, or support fitting, or jig, or fixture, uponwhich the workpiece is mounted has at least one degree of freedom ofmotion. In the example shown, the degree of freedom of motion isrotational motion about the longitudinal axis of mandrel 28, such thatcap 30 is spinning, as notionally indicated by arrow ‘A’. As notedabove, in general a workpiece may be mounted on a seat or jig and movedin some manner be it rotational or translational in the x-y plane.Mandrel 28 and apparatus 22 are both connected to an electrical powersource, such that they are of opposite polarity. When electrode 24 isbrought into contact with electrode cap 30, electric current will flowbetween them. Inasmuch as current flow is initiated by a spark as thetwo parts come into proximity, and inasmuch as both parts are moving,contact may be intermittent, and at each contact a portion of electrode24 may melt or otherwise be deposited upon cap 30. As cap 30 spins andelectrode 24 makes and breaks contact, the top of cap 30 becomes coatedwith the electrode material. Cap 30 may be a copper cap, it may have afirst coating of nickel; and the TiC or TiB₂, or other coating material,may be laid down on top of the nickel. Handle apparatus 20 may be avibrating apparatus, such that the tendency to make and break contactwith the object workpiece is enhanced.

Considering again apparatus 20, there is housing, or backshell, or haft,or body generally indicated as 32, that housing including first andsecond portions 34, 36, which may be referred to as backshell halves.First and second housing portions 34, 36 are held together by an arrayof fasteners such as may be in the nature of threaded cap screws 48.Both backshell halves may have porting in the nature of vents such asinlet vent array 38 and outlet vent array 40, by which air or other gascoolant may be admitted to, and enabled to depart from, the interior ofhousing 32. The backshell halves may be made of an electricallynon-conductive, or electrically insulating, material. The girth ofhousing 32 may be suitable for being grasped in the hand of an operator.Although not necessarily circular in section, as seen in FIG. 6, thegeneral proportions of housing 32 are that it may have a throughdimension of the order of 2 inches.

At the connected end, housing 32 has three input connections, the firstinput being an electrode power connection, which may be a DC powerconnection, indicated as 42, and which may, ultimately, be connected toan ESD power source—the same power source of which the opposite pole isconnected to mandrel 28. The power source may be indicated genericallyas a power supply 200, discussed below. The second input is a motorpower source 44 for operation of an electric motor within housing 32, inthe form of a power cable which may be 120V AC 60 Hz, or 220 V AC 50 Hz,or a 12V DC source, or such other source as may be, and could be apneumatic source. The power may in some embodiments also be provided bypower supply 200. The third input is a cooling line 46, such as may bean air line. At the free end of housing 32 (i.e., the end distant fromthe three connection inputs) is the tool holder assembly, indicatedgenerally as 50, and described in greater detail below.

Considering FIGS. 4 and 5, an internal machinery space 52 is definedwithin the two halves or portions 34, 36 of housing 32. The inputs passinto housing 32 at an opening 54. Opening 54 may be located at the firstend of housing 32. It may be that roughly half of each opening is formedin each portion of the housing, the perimeter of the opening beingclosed together when the halves are assembled. There could,alternatively, be a separate opening for each input as may be, and suchan opening or penetration could be formed entirely in one half theshell. The main power cable, namely that of electrode power connection42, is secured at a terminal lug 56 inside housing 32, adjacent toopening 54. The coolant conduit may have the form of a hollow pipe 58that is formed to run along the inside proximal margin of housing 32,with an outlet 59 oriented toward tool holder assembly 50 adjacent theseat of electrode 24. Coolant conduit 58 may be used to carry air as acooling fluid, or, alternatively, it may be used to conduct an inertgas, such as argon, to electrode rod 24, and, whether used for coolingor not, may be used for the alternate purpose of providing an inert gasshielding to the coating process. That portion of pipe 58 lying outsideof opening 54 may be made of a non-electrically conductive material suchas a plastic tube. That portion of pipe 58 lying within housing 32 maybe made of a metal, such as copper, aluminum, stainless steel, mildsteel, or such other metal as may be suitable, those metals tending tohave higher thermal conductivity than plastic pipe.

Also connected at terminal lug 56 is a predominantlylengthwise-extending member defining a transmission 60. Assembly 50 ismounted to the far end of transmission 60. Transmission 60 may have theform of a lever or spring or beam 62. The first end of the spring orbeam is secured at terminal lug 56, as indicated. The main or medialportion of transmission 60 may lie next alongside pipe 58 and may becontained between pipe 58 and a fulcrum 64 located intermediate thefirst and second ends of transmission 60. In the embodiment illustrated,fulcrum 64 is located closer to tool holder assembly 50 than to lug 56.The position of fulcrum 64 is adjustable according to the variouspositions of an array of mounting fittings, which may be threaded blindsockets, indicated generally as 66. If the length of transmission 60from the center of lug 56 to the axial centerline of tool holderassembly 50 is designated as “L”, the position of fulcrum 64 may be inthe range of about ⅗-⅘ of L from lug 56 to assembly 50. That portion oftransmission 60 lying beyond fulcrum 64, i.e., between fulcrum 64 andtool holder assembly 50, is a cantilever. Tool holder assembly 50 actsas a concentrated mass at the end of the cantilever. Transmission 60 sorestrained has a configuration like a spring-board or diving board.

Tool holder assembly 50 has a first portion 72, and a second portion 74.The distal end of transmission 60 has an aperture formed therethrough somale portion 76 of first portion 72 can mate with the female portion 78of second portion 74, with the end of transmission member 60 sandwichedtherebetween. It is arbitrary which of portions 74 and 76 is male andwhich is female, the parts are joined in a connection. As matedtogether, tool holder 50 is rotatable about its long axis to permitelectrode 24 to be turned. First portion 72 may be a locking socket orchuck defining the seat 80 for electrode 24, and may have tightening orsecuring members, such as a grub screw 82. Second portion 74 includesspring-biased graphite brushes 84. A handle 86 is mounted to secondportion 74, the handle having an appropriate grip by which it may beturned, such as by a person wearing gloves. Handle 86 may be made of anelectrically insulating material, such as a cast plastic. First portion72 and second portion 74 are both electrically conductive, and may bemade of copper or a copper alloy. Consequently an electricallyconductive path is completed from electrical power connection 42 throughtransmission 60, through brushes 84, through second portion 74 and firstportion 72, and into electrode 24.

Also within housing 32 is a vibration assembly, or oscillator, orshaker, or motion exciter such as may be identified as 90. It mayinclude a motor 92, which may be an electrical motor connected to motorpower source 44. Motor 92 may drive an output shaft 94 that passesthrough near and far bearings 96, 98. An eccentric 100 is mounted toshaft 94, such as at the distant end thereof. Eccentric 100 may be adisc with either an unbalanced weight or an unbalanced cavity indicatedat 102, such that when shaft 94 rotates, assembly 90 vibrates. Theresultant vibration has an amplitude having a component in the axialdirection of electrode rod 24. An air moving device, such as a fanblade, or impeller 104 is mounted to shaft 94, and, as shaft 94 turnsimpeller 104 draws air in through inlet vent array 38, and urges it outthrough outlet vent array 40. In an alternate embodiment, the directionof the airflow may be in the opposite direction.

In use, an operator grasps housing 32, and uses electrode 24 much like apencil to paint or coat the workpiece object. While this is occurring,the rotation of eccentric 100 causes apparatus 20 to vibrate, which, inturn, causes electrode 24 rapidly and repeatedly to make and breakcontact with the work piece. With each oscillation there is a new sparkand deposition of the material of electrode rod 24 onto the workpiece.

Vibration assembly 90 provides a forcing function input to transmission60. Transmission 60 is not merely an electrical conductor, but also amechanical conductor or resilient transmitter in terms of transmittingan input impulse, or wave-train of impulses. The force and displacementtransmissibility of transmission 60 of the mechanical motion of theforcing function input to electrode holder 50 is dependent upon thenatural frequency of the vibrational degree of freedom of interest. Forexample, in assembly 50 the axial direction of electrode 24, thatdirection being the same direction as the dominant vibration mode of thespring board or beam of transmission 60 as it flexes outboard of fulcrum64. Although the axis of the cylindrical rod of electrode 24 is shown asbeing perpendicular to the long axis of apparatus 20, this need notnecessarily be so. In another embodiment, electrode 24 may have the formof a rod having an axis parallel to, or concentric with, the main bodyof housing 32.

The handle apparatus drives the consumable electrode 24 to vibrate in afirst degree of freedom of motion in longitudinal or predominantlylongitudinal movement (i.e., having a component of motion, possibly apredominant component of motion in the direction of the longitudinalaxis of the electrode rod) relative to the metallic surface being coatedor treated in the process. The longitudinal force or displacement isgenerated by attaching an eccentric circular metal load to a spinningmotor. The positioning of the eccentric weight determines the poundingor contact force when the contacts are made. The frequency of vibrationis controlled with the speed of the motor to which the eccentric weightis mounted, and the amplitude of vibration may be affected by theplacement of the fulcrum. The longitudinal movement of the consumableelectrode in a direction that includes a component of motion, andusually a predominant component of motion, normal to the surface to betreated, allows the periodic contacts to be made with the metallicsurface of the workpiece. This occurs while that workpiece surface isbeing driven in a second degree of freedom of motion. The combination ofmotions, and the vibration-driven urge to make and break contact, mayresult in a relatively stable or consistent sequence of electro-sparks(when the contacts open) and depositions of coating material (when theopen contacts approach) that take place in the process. The vibratingmotion is, or includes, motion normal to the surface being coated, andoccurs at the same time as the surface is being moved in another degreeof freedom, e.g., as by rotating about an axis, or by translationalmovement relative to the normal direction, such as to bring a “fresh”portion of the work piece under the coating rod.

This process may be compared with a known process in which only theworkpiece is moving, e.g., by rotation, and the coating electrode rod isheld against the surface, or in which the workpiece is stationary, andthe electrode rod is spinning about its axis. The coating material tendsto be much harder than the copper or other material being coated (which,if copper, may itself have a nickel overlay). In the existing process,there may be a grinding effect of the hard coating material, tending toremove the soft material in the ESD process, including a fair portion ofthe previously deposited coating material that one might wish to retain.Such a process may not be as efficient as might be desired. By contrast,the axial vibrating motion of rod 24 normal to the surface may tend tofacilitate relative translation of the workpiece between electrosparks,possibly without the same grinding effect, and perhaps with a greateroutput yield for a given quantity of coating rod consumed.

The embodiment of electrode handle apparatus 120 of FIGS. 7-9 issubstantially similar to the embodiment of electrode handle apparatus 20of FIGS. 1-6, and, to the extent applicable, common parts are identifiedby common part numbers. Apparatus 120 differs from apparatus 20 to theextent of employing a servo motor 122 carried on a motor mount 124seated in housing 126. Servo motor 122 may be a brushless DC (BLDC)servo motor. Servo motor 122 is a variable speed motor. A separate shaft130 is carried in a first, or mid-position bearing 132 and a second ordistant position bearing, or pilot bearing 134. An imbalance weight 136and adapter 138 are mounted on the distal end of shaft 130 (i.e., theend distant from motor 122), and correspond to eccentric 100. Animpeller 140 and impeller adapter 142 are mounted to shaft 130 betweenthe front and mid bearings (i.e., bearings 134 and 132). The proximalend of shaft 130 is connected to the output shaft 144 of motor 122 by aflexible coupling 146. Flexible coupling 146 may tend to isolate motor122 from radial loads on shaft 130.

Further, apparatus 120 has a movable fulcrum 150 that is externallyaccessible, and adjustable by means of access slot 152 and set screw154. As previously, the ability to move fulcrum 150 longitudinallytoward tool holder assembly 160 may tend to permit the cantileveredportion of transmission 60 to be choked down, both by shortening thelength of the cantilever, and by constraining its lateral motion.Fulcrum 150 may, in that sense be said to choke down, or damp down, theamplitude of vibration of tool holder assembly 160 in direction ‘B’,namely the axial direction of rod 24.

An alternate electrode handle apparatus 220 is shown in FIGS. 10-14.Apparatus 220 may be taken as being the same, or substantially the sameas apparatus 20, to the extent that similar parts may be indicated withthe same item numbers, and the foregoing description may be taken toapply to the features of apparatus 220.

Apparatus 220 differs from apparatus 20 in a number of features. Aspreliminary points, although apparatus 220 does not show a third input,namely cooling line 46, it may be understood that apparatus 220 mayinclude such a line in other embodiments. Electrical power connectionline 44 feeds electrical power from a power source to motor 92.Apparatus 220 includes a flexible couple or connection or clutch ordamper, indicated as connection 230. Connection 230 may include a springor resilient member such as may tend to provide a dynamic filter betweenmotor 92 and the eccentric weight 100. Connection 230 is mounted to theoutput shaft of motor 92. Driven shaft 232 is connected to, and extendsfrom connection 230 to an impeller 104, and, in turn, to eccentricweight 100. As motor 92 turns, impeller 104 draws ventilating airthrough inlet apertures or vents or ports 38, across motor 92, andforces it out exhaust ports 40. Driven shaft 232 is carried in front andrear bearings 234 (axially near motor 92) and 236 (axially more distantfrom motor 92), with weight 100 being mounted axially outboard ofbearing 236. The axial spacing of bearings 234 and 236 may provide along moment arm, and may tend to aid in resolving the eccentricimbalance into the housing, or housing body, 240 through bearings 234and 236 rather than through the bearings of motor 92. Motor 92 may havean on-off switch or speed control as shown on the dorsal portion ofapparatus 220 at 238.

Housing body 240 may be open at the head or front end, (i.e., the endnearest electrode 24) as at 242. Housing body 240 may have left andright hand parts of halves 244, 246, that fit together, as above, andthat may have indexing pins and blind sockets for that purpose. One orthe other of halves 244, 246 may include an access port or keyway 248through which a tool, such as a screw driver, socket, wrench, or Allenkey, may be introduced to tighten or loosen the securing fastener, suchas a grub screw, of eccentric weight 100. To the extent that end 242 isopen, eccentric weight 100 may then be removed or replaced, as may bedesired or suitable for the speed of operation such as may be set oradjusted with speed control 238.

Further, apparatus 220 may include an externally adjustable fulcrum, orseat, or snubber, or damper 250 that, when secured, bears against themotion transmitting member to which electrode 24 is mounted, such asspring 62. In essence, damper 250 functions as a guitar fret, changingthe natural frequency of the cantilever of spring 62, and also as anamplitude limiting device, to the extent that damper 250 confines spring62. Damper 250 may include a rubber (or other polymer or elastomer)body, and may have a wedge shape. The fastener 252 of damper 250, andits range of adjustable locations, is seen in FIG. 13.

Further still, apparatus 220 includes a different electrode holdingfitting or seat, 260. While handle 258 may still be rotated about itslongitudinal axis by virtue of its rotatable mounting 262 to spring 62,a split collar 264 has left and right jaws 266, 268 that seize upon theend of electrode 24, and are secured by a chuck, or lock, or lateralfastener 270. The jaws of apparatus 220 may tend to hold a smallerportion of rod 24 than the fitting of apparatus 20, thus tending toreduce the wastage of the expensive sintered coating composition rods.

A further alternate embodiment is shown in FIGS. 15 a and 15 b in whichthere is a vibrating handle apparatus 280. Apparatus 280 issubstantially the same as apparatus 220, and may be taken as being thesame except as noted. Apparatus 280 differs from apparatus 220 to theextent that housing 282 of apparatus 280 has in both left and right handhalf-shells a forwardly extending bulge, or protrusion, or head,indicated generally as 284, that defines an internal chamber oraccommodation 286. Accommodation 286 provides a seat for a motor 288.Motor 288 may be a brushless DC servo-motor. The axis of rotation of theoutput shaft of motor 288 is aligned with the axis of rotation ofelectrode rod 24. The output shaft of motor 288 is connected to thechuck (i.e., mounting 262, and jaws 266, 268) that hold rod 24 by aloose-splined fitting or coupling 290. Coupling 290 tolerates relativeaxial displacement of rod 24 as spring 62 vibrates. Motor 288, when inoperation, may turn at a relatively slow speed. The speed of the outputshaft of motor 288 driving the chuck may have a chuck speed in the rangeof 40-120 rpm, and may in one embodiment have a speed of about 60 rpm.Motor 288 need not be activated, and may be programmed for a singleoutput speed, a choice of output speeds, or a continuously variableoutput speed such as may be controlled by the operater's inputs.

In the examples of apparatus 20 and apparatus 220, there may be animplicit assumption that the workpiece is moving, such that it has (atleast) a single degree-of-freedom of motion, e.g., rotational spinningabout an axis as indicated by arrow ‘A’ in FIG. 1. In addition there isat least a second degree-of-freedom of relative motion between electroderod 24 and workpiece 30 by virtue of the vibration of rod 24 driven bythe mechanical forcing function oscillator, (i.e., driven eccentricweight 136 input to spring 62, for example).

It may be that the workpiece to be coated or treated is not a weldingcap spun about the axis of the body of revolution. The workpiece may notbe a body of revolution. It may be that the workpiece is stationary, or,alternatively, that the workpiece is constrained to other degrees offreedom of motion, such as motion in an x-y plane, which may be linearmotion along an axis in that x-y plane. That motion may be periodic andmay be reciprocating. In the example of apparatus 280, quite aside fromthe manner in which the user manipulates the handle, the handleapparatus has both first and second degrees of freedom of driven motionin terms a driven function in reciprocating axial translation due tovibration, and a second degree-of-freedom of driven motion in rotationabout the axis of rod 24. In this embodiment, whether the workpiece isstationary or not, the (at least) two-degrees-of-freedom of relativemotion is provided by apparatus 280 in any event. Further, whateverorientation may be used by the operator, it is thought that rotation ofrod 24, even relatively slow rotation, about its axis, may tend topromote more even consumption of rod 24 as a function of circumferentialangular orientation of rod 24. That is, as rod 24 rotates it may tendcontinually to present “fresh” rod material to contact the work piece,and may tend to be consumed evenly.

ESD Surface Modifications

As noted above, crack formation and delamination are known phenomena inelectrode coating processes (See FIGS. 18 b and 18 c). There aredifferent approaches to treating the ESD coating to reduce or to attemptto eliminate defects such as may be found in the coating. However, ESDcoatings treated by post-processing may require expensive tooling andprocedures. In an alternate approach described herein, an in-process ESDcoating treatment action may occur during the coating process,substantially simultaneously. In this process the ESD power source 200has an output that alternates between an ESD phase, or step, orduty-cycle portion, or period; and a peening power during the surfacecoating process as suggested by the alternating coating and peeningstages 202, 204 in FIG. 17 a.

It has been observed by the inventors that peening the surface coating206 using the same vibrating applicator may cause plastic deformation ofthe coating, and, in so doing, may tend to close up the gaps or cracks208 and reduce the number of delaminations 210 in the coating. That is,when the electrical power provided is reduced, as by reducing thevoltage to a second voltage, V₂, below the voltage at which arcing caninitiate, defined as the ESD initiation voltage, or first voltage, V₁,the melting of the approaching rod may tend not to occur. Instead, inthe period of time in which contact is broken between the electrode rodand the workpiece no electrical current flows. Thus both rod 24 and thepreviously deposited material cool rapidly. However, while thetemperature may still be high, it may not be high enough for the coatingmaterial to remain molten. Although below the melting point of thedeposition material, and no longer molten, the coating may still be at atemperature at which the coating is soft and plastic, i.e., not fullyhardened. At this elevated temperature striking the coating may tend tocause plastic deformation of the coating, which may tend to force closedcracks in the surface, such as cracks 208. It may be more effective tomodify the surface, defects in the coating when the temperature of thecoating is high, but not high enough to be molten.

As suggested in FIGS. 16, and 17 a-17 d, the ESD power source has acontroller indicated generally as 212 that is capable of operation attwo (or more) different levels of output power or voltage, or in (atleast) two different modes of operation. There may be a first mode ofoperation, which may be termed an ESD coating mode corresponding tostage 202, in which the voltage differential V between the electrode rodand the electrode workpiece to be coated may be established at a firstlevel, or first magnitude, which may be a voltage sufficient to causearcing between the rod and the workpiece when they are brought intoproximity with each other, and are then in contact. This is a depositionmode in which the coating materials melts and “splashes” onto theworkpiece (See FIG. 18 a). The deposition mode starts at a time x₁ atthe ESD initiation voltage, although that voltage may drop rapidly asdeposition occurs. The physical motion of the moving rod, e.g., due toan imposed mechanical vibration forcing function such as oscillation ofhandle apparatus 20, may then break the contact, ceasing the currentflow, and ceasing deposition at time x₂ the time interval of depositionthen being x₁−X₂=t₁.

Power supply 200 may then sense the cessation of current flow, and,given that sharp and sudden interruption in current, may drop themagnitude of the output voltage to electrode rod 24. This may be done byswitching off the switch T1 that is connected to a first or maincapacitor (or capacitor bank), C1, that is typically charged (andre-charged, as may be) to the ESD initiation voltage by ESD PowerControl 214 typically by switching the controlling switch or transmitterT₁ to the “off condition”, and by switching to another branch of thecircuit having a capacitor (or capacitor bank) C2 whose initial chargeis at a second, lesser selected voltage V₂ typically by switching thecontrolling switch on transmitter T₂ to the “on condition” Voltage V₂.charged and recharged across capacitor bank C2 by a Peening PowerControl 216. Contact remains open over time period t₂. When the rodagain approaches the workpiece and makes contact as at time x₃, thepeening voltage is applied and current flows until contact breaks.

During the discharge phase, the power supply to the first capacitor bankis interrupted, i.e., shut off, so that the power supply does not supplypower to C1 during discharge. Only once T1 has been opened (i.e, turnedoff), after the discharge phase of C1, is power reconnected to chargeC1. Similarly, switch T1 does close (i.e., turn on or activated) untilC1 has been charged to the programmed voltage threshold, (in thisexample, the ESD spark initiation voltage). Thus only once the capacitorbank has been fully charged is the apparatus enabled to discharge byturning “On” switch T1, at which time further charging current from thepower supply is also inhibited. Thus the logic for switch T1 to beturned on requires that two conditions be met: first, that C1 has beenchanged to V1; and, second, that the time period counted out by theclock between the most recent previous step has expired.

When switch T1 is activated to the “On” condition, the next time thatthe tip of rod 24 approaches the workpiece, discharge will ensue.

Similarly, the second capacitor or capacitor bank, C2, cannot bedischarged unless it has been fully charged to its programmed or presetthreshold voltage, V2. Switch T2 is only activated to the “On” conditionwhen C2 is fully charged, and the pre-set timing gap between the mostrecent current flow has expired.

It follows that T1 and T2 are not “On” at the same time, although theymay both be “Off” during the timing intervals between a T1 or T2 currentflow cessastion and the next succeeding T2 or T1 current flowcommencement. While, in general, the time duration of each successive T2or T1 “On” condition may be individually varied, they may typically bethe same. Similarly, while the duration of the gap period (where neitherT1 nor T2 is “On”, but rather, both are “Off”) may be individuallyvaried it is convenient that they be uniform. Further, while the “On”and “Off” periods may differ, they may typically be of about the sameduration, that duration being typically of the order of 1 mS-5 mS, and,in one embodiment, about 2 or 3 mS. The gap period may be very short,particularly where more than two capacitor banks are employed.

In one embodiment the second or lesser electrode voltage may be cut tozero. In another embodiment the magnitude of the second output voltageV₂ may be different from, such as being cut below, the ESD initiationvoltage V₁, to a non-zero level at which current may flow on contact,and so a heating or warming effect may take place, but not so muchheating as to cause melting. The warming may prolong the time duringwhich the coating remains suitably soft for plastic deformation. In thissecond mode the voltage differential between the power supply output tothe rod and the workpiece connection to the power supply may becommenced at, and continue at, a level that is less than, and may besubstantially less than, of the ESD initiation voltage at commencementof discharge. In some embodiments it may be less than V2 of the ESDinitiation voltage. For example, in some embodiments the first voltagemay be in the range of 25 to 50 V DC and may in one embodiment beapproximately 30 V. The second voltage may then be chosen to be a valueof less than 30V, such as 0-30 V, and in one embodiment may be about 20V(or roughly, up to about ¾ of the first ESD initiation voltage, and inone embodiment about ⅔ of that initial voltage). In the first dischargecircuit, there stored charge on the capacitor C1 is connected directlyto the terminal, i.e., there is no intermediate current-limitingresistive element. Once arcing occurs, the discharge may have the formof a very rapid spike in which voltage drops rapidly. In the process,ESD Power Control supply 214 This lesser voltage may also decay somewhatover the contact time of the rod with the workpiece with the use of aresistor R1 mounted in series with the thyrister, or switch, T2. Thusthere is a first mode at a first voltage or first power, and a secondmode at a second, lesser, voltage or lesser power. In one embodiment theoperator may set the selected first and second voltage levels V₁ and V₂.

Contact may again be broken when further motion of the welding rodoccurs, as due to the mechanical vibration forcing function of thehandle. Again, the power supply may sense the abrupt cessation ofcurrent flow, and may use that step change signal again as a signal, ordatum, or indexing feature, or trigger, or triggering event to alter thevoltage supplied. For example, in response to that triggering event, C2power supply may switch off the second capacitor or capacitor bank C2 byswitching off switch T2, (such that C2 may revert to a charging orrecharging mode powered by Peening Power Control 216); and may revert tothe first capacitor C1, such that a new deposition period or step orstage, or duty cycle, may commence.

Alternatively, power supply 200 may switch to a third capacitor, orcapacitor bank which may be at either the same initial voltage as C1 (inthe event that C1 is still recharging and a fresh, fully charged ESDinitiation voltage charge is required); or the same voltage as theinitial voltage of C2 (in the event that a fresh lesser voltage chargeis desired); or a third voltage, that is different from either of them.For example, the initial voltage of C2 (or a cut-off condition of novoltage to the electrode holder, whether there is a sec/ond bank ofcapacitors or not), may be zero. Alternatively that second voltage, orpower level, may be quite low because the newly deposited coatingmaterial remain very hot, and needs little or no additional heat whenthe rod approaches to contact it for a second time. It may be that bythe third period of contact, the deposited material may be somewhatcooler than it was during the second contact period, and so it may bethat more heating than previously is desirable to slow cooling such thatthe surface coating may remain plastic, or more easily made plastic.Thus the third voltage may be higher than the second voltage, and yetstill well below the level of voltage and power such as might cause thecoating again to become molten. The schedule of first, second, and thirdvoltages may be pre-programmed into the power source controller, or thevoltages may be selected by the user.

After being contacted for a third time, contact may be broken again dueto the motion forcing function of the electrode holder. Once again, thesensors of the power supply, monitoring current, for example, mayindicate a step change in current (i.e., a drop to zero) when contact isbroken, and voltage may be switched “off” or “on”, accordingly inrespect of the next branch of the circuit. There may be several lowvoltage or zero voltage impacts of the rod with the work piece. Howevermany “cold” impacts there may be, be it one or more than one, after aperiod of time the process may start back at the beginning with C1 and ahigher voltage, namely the ESD spark initiation voltage, such as tocause additional new coating material from the electrode rod to bedeposited on the work piece.

In the process described above, the power supply may tend continuouslyto be sensing and evaluating current flow as a means to triggerswitching or altering of voltage levels supplied to electrode rod 24. Inan alternative to the process described above, the speed of rotation ofthe workpiece may be known, and the frequency of vibration of the motionforcing function of the vibrating handle may also be known, such thatthe period of time between successive contacts, and breaks of contact,between the electrode rod and the workpiece is known, at least in anapproximate sense. With the frequency of vibration being known, thepower supply may be programmed to run at the first voltage for a givenperiod of time, that period of time being at least as great as onewavelength of the forcing frequency. That is, if the forcing frequencyis 100 Hz, then the time of C1 voltage “on” would be at least 10 ms.That period may then be followed by a period of time at least as long asone wavelength of the forcing frequency in which the C2 voltage isapplied. In the event that there is a third voltage, the power supplymay follow the second period of time by a third period of time of atleast one wavelength at the third capacitor bank voltage, and so on, foras many time periods and voltage variations as may be.

In the embodiments described, the nature of the deposition step isdifferent from the nature of the non-deposition step. In the depositionstep, the action is, substantially, a discharge of accumulated chargeagainst a very low, or approximately zero, resistance. The essence ofthe step is a capacitive discharge. It may be characterized as a spikethat commences at V1, and in which the current is very large, but ofshort duration at a rapidly falling voltage level. By contrast, thepresence of resister R1 in the second circuit, namely the circuit ofswitch T2, may tend to be current limiting. R1 may have a resistivevalue in the range of ½ to 2 or 3 Ohms. The current flow in that secondstage or phase or portion does not then approximate a sudden surge orspike of an unrestricted capacitive discharge, but rather a portion,perhaps an initial portion, of a controlled capacitive decay curve withan RC time constant, that constant being a function of the product ofR1×C2. That decay curve commences at V2. Where the time period ofcontact is very short, the end voltage may be relatively close to V2.While there may be an initial very short period of a spark during the T2“On” phase or stage, given the voltage drop across R1 the phenomenon isone of high current flow heating the coating during contact, as opposedto an arcing phenomenon.

In the process, the welding electrode cap to be coated may be spinningor turning at some rotational speed. That speed of rotation of theworkpiece may be of the order of as low as about 200 rpm, and may be ashigh as 1200-1800 rpm. In one embodiment it may be about 300 rpm toabout 600 rpm. It may be driven by a motor running at 1725 rpm through areduction drive. The BLDC motor of the oscillator drive in the vibratinghandle may run at speeds in the range 15,000-20,000 rpm, and in oneembodiment may be about 18,000 rpm, or 300 Hz. The mean contact time ofthe rod with the electrode cap such as t₁, t₃, t₅, etc., may be in therange of 1-10 mS, and in one embodiment may be about 3 mS. In generalt₁=t₂=t₃=t₄=t₅=t₆, although this need not be so. That is, the meancontact time need not be equal to the mean dis-engagement time. Thecontact time while melting and depositing material may vary from thecontact time while peening the coating.

The hammering or repeated mechanical impact process that occurs whilethe voltage is reduced (or cut to zero), may be termed “peening” of thecoating, and may be associated with a lower, peening power level. NormalESD electro-spark depositions are formed during the coating cycles (orperiods). The peening actions used to modify the surface coating layerare introduced during the peening periods or reduced power. As describedabove, the output of the ESD power source is switched to a differentpower level, which could be zero voltage, during the Peening cycles(periods). The already-deposited surface is modified by the peeningactions. That is, while the coating material is still warm, immediatelyafter deposition, the vibrating action of the electrode rod, driven bythe vibrating handle, contacts the deposited surface, tending to make itan impact surface. As the name may suggest, the surface is thought toundergo a “peening” or hammering during the repeated impacts. Plasticdeformation of the cooling, formerly molten and temporarily deformablesurface may tend to reduce, or close up, cracks and may discouragedelamination that may have occurred during, or to have arisen from theESD coating actions. While peening may occur with no electrical currentto the electrode rod, the use of some continuing current as a peeningpower level may tend to to maintain the temperature of the spot underthe peening actions and thereby slow the cooling process, such as maytend to allow a longer time period in which the coating may be locallyplastically deformed. The peening power electrical voltage and currentlevels may be adjusted depending on the coating subjects andapplications.

The power source, or power supply described above may be used toimplement the in-process coating and peening actions during the coatingprocess. That is, the dual action ESD power source is able to deliverthe voltage or power for the regular ESD actions, and also to deliverpower (electrical power could be zero) for the peening actions.

The Dual Action ESD power source or power supply 200 includes thefollowing modules:

-   -   ESD Power Control 214: for the voltage control of the ESD        capacitor, C1.    -   Peening Power Control 216: for the voltage control of the        Peening capacitor, C2.    -   Dual Action Control Unit 218: for the voltage control of the ESD        and Peening capacitors; also the switching control of the ESD        and Peening power outputs.    -   User Panel 215: for the programming of the ESD and Peening        capacitor voltages; and the control pattern of the ESD and        Peening actions.

The ESD and peeing output pattern is programmable by setting someparameters via user panel 215. This may permit flexibility for thecontrol of output patterns in different application environments.

The length and frequency of the coating and peening periods areadjustable, and may depend on the target coating subjects and materials.There power level may also be adjusted according to variations in thenature of the coating and peening action and these parameters aredependent on the target subjects and materials.

Surface coating modification methods may employ ultrasonic pressurizedrotating friction process. This method may be used to encourageimprovement of the density of the coating layer material and the bondingof the coating material to the base metal of the substrate. This processmay be applied in respect of the coating of welding electrodes. Coatingelectrodes, or other surfaces.

Material of FIGS. 18 d-18 h, 21, 22, 23 and 24

FIGS. 21, 22, 23 and 24 show details of an apparatus for themodification of surface coatings on resistance welding electrodes. Thatis, in the example the workpice may be a welding electrode cap. The capmay have a coating. The coating may be a TiC coating. The workstationfor the clamping and rotation of the workpiece may include a work benchA; an equipment frame 302; an electric motor 303; a transmission belt304; a pulley 305; a supporting bearing 306; a transmission shaft 307; aclamping chuck 308 for holding the workpiece, and guiding rails 309 and310. Components of an integrated ultrasonic rotating friction headassembly may include sliders 311; a lower panel 312; a screw shaft 313;an upper panel 314; an ultrasonic positive power terminal or input 315;an ultrasonic negative power terminal or input 316; a bushing or brushor sliding conductor 317; bearings 318; a belt pulley 319; atransmission or drive belt 320; an electric motor 321; an ultrasonictransducer 322; a transducer horn 323; a rotating friction head 324; ahousing 325 and a slider 326. Components of the ultrasonic power sourcemay include an ultrasonic power source positive terminal or output 327;an ultrasonic power control knob 328; an ultrasonic power sourcepositive output 329, and an ultrasonic power source power switch 330.

The following is a description of an apparatus and method for postdeposition treatment of a coated resistance welding electrode, as shownin FIGS. 21, 22, 23 and 24.

A work table A is employed for the clamping of the workpieces. Table Amay have an equipment base or frame 203, an electric motor 303, amechanical transmission or drive belt 304, a pulley 305, a supportingbearing 306, a transmission shaft 307, a clamping chuck, or tool-holder,in which to hold the workpiece 308, a first track or guide rail 309 anda second track or guide rail 310.

The integrated ultrasonic rotating friction head assembly B (which mayin essence be apparatus 20, 120, etc.) may have a slider 311, a lowerpanel 312, a screw shaft 313, an upper panel 314, an ultrasonictransducer positive input terminal 315, an ultrasonic transducernegative input terminal 316, a brush or shoe, or sliding conductor 317,bearings 318, a belt pulley 319, a mechanical transmission or drive belt320, an electric motor 321, a transducer 322, a transducer horn 323, arotating friction head 324, a housing 325 and a slider 326.

An ultrasonic power supply C may include an ultrasonic output positiveterminal 327, an ultrasonic output power knob 328, an ultrasonic outputnegative terminal 329, and an ultrasonic power switch 330.

The apparatus may include the integration of the combined apparatus ofassemblies A, B and C. Electric motor 303 of the workstation A is fixedto, or mounted to, the main machine frame 302. Drive power from theoutput shaft of electric motor 303 is coupled to drive transmissionshaft 307 in rotation through the transmission belt 304, pulley 305 andsupporting bearings 306.

The workpiece having a surface coating to be treated or modified ismounted to, or in, clamping chuck 308. Clamping chuck 308 is connectedto the transmission shaft 307, such that operation of motor 303 maycause corresponding driven rotation of chuck 308. Guide rails 309 and310 of module A are fitted to, or mated to, or engaged with, sliders 311and 326 respectively of the integrated ultrasonic rotating friction headassembly B.

Pressurized rotating friction motion from rotating friction headassembly B can be repeatedly applied to the surface coating on theworkpiece 301 as required for the processing procedure. In thisdescription the term “pressurized” may tend to mean pressing or forcing,or biasing, the coating apparatus against workpiece 301 under somebiasing force, where at least a component of the force is normal to thesurface of workpiece 301 at the location of contact of the coatinginterface, such that the coating apparatus is biased against theworkpiece such that relative motion (e.g., including a component ofmoton tangential to the normal vector defining the line of contact ofthe surfaces) between them will give rise to friction between thecoating apparatus and the workpiece surface, e.g., in the tangentialplane to which the normal vector of the surface is perpendicular.

Upper panel 314, which is mounted with the rotating friction headassembly, is connected to lower panel 312 through the coupling of screwrail 313. Rotating friction module B can be driven up and down with theuse of the screw shaft of screw rail 313. Application of certainpressure, or force, of or against, the coating surface of workpiece Acan also be achieved with simultaneous rotational motion, be it ofworkpiece A or of the coating apparatus. The positive 315 and negative316 terminals of the ultrasonic transducer are connected to the outputpositive 327 and negative 329 terminals, respectively, of ultrasonicpower supply C. Sliding conductor 317 is connected to transducer 322with the use of a pair of electrical wires. Transducer 322 is connectedto the transmission horn 323 for the transmission of ultrasonic energyto rotating friction head 324.

The shape of the top of the friction head could be flat or curvedaccording to the requirement of the workpiece. Ultrasonic pressurizedrotating friction, i.e., friction at the contact interface of therotating surface under a biasing force normal to that surface, can beapplied onto the coating surface of workpiece 301 with the use of theintegrated friction head assembly. The rotation is driven throughelectric motor 321, driving belt 320, belt pulley 319 and bearings 318.

In this application example, on workstation A, the transmission shaftthat is mounted with a clamping chuck is driven in rotation by theelectric motor through the coupling of transmission belt, pulley andbearings. The integrated ultrasonic rotating friction head assembly canbe moved vertically through the fitting of the two sliders on the lowerpanel with the two guiding rails on workstation A. The rotating frictionprocess can be applied to the workpiece repeatedly.

In this embodiment, the ultrasonic rotating friction head assembly isattached to upper panel 314 which is connected to lower panel 312through screw shaft 313. The screw shaft serves two purposes, namely,first, to move the ultrasonic rotating friction head assembly vertically(up and down); and, second, to apply pressure, or a biasing force, toworkpiece A.

The ultrasonic rotating friction head assembly is driven in rotation bythe electric motor through the coupling of the belt and bearings, suchthat the workpiece rotates. It is also driven to make contact and applypressure, that is a biasing force, to the workpiece through the controlof the screw shaft. With the application of ultrasonic vibration, theapparatus is able to perform ultrasonic pressurized rotating frictionprocessing to the surface coating of the resistance welding electrodes.That is, while the apparatus is under the biasing force againstworkpiece A, and while there is rotating friction, ultrasonic vibrationis also being applied and transmitted across the same contact interface.

The following gives the procedure of the ultrasonic pressurized, orforce-biased, rotating friction process:

-   -   1) The welding electrode is mounted to the clamping chuck        properly.    -   2) Turn on the power to the workstation, ultrasonic power source        and the rotating friction head assembly.    -   3) Adjust for proper pressure, i.e., biasing force, workpiece        rotational speed, rotating friction head speed, and ultrasonic        power level.

The rotating friction head, with external pressure (i.e., biasing force)and ultrasonic vibration is then used to treat or modify the surfacecoating of the welding electrode, or to such other coated surface as maybe. The rotating friction head is moved, or translated, or reciprocated,along guide rails 309, 310 to cover the complete surface of the coatingon the welding electrode. The power is turned off when the process isfinished.

In this example application, the ultrasonic power may be about, or is100 W; ultrasonic frequency may be about, or is 50 kHz; pressure (i.e.,biasing force) on the surface coating from the rotating friction headmay be about, or is, 200N; rotational speed of the rotating frictionhead may be about, or is 1400 rpm. For a welding electrode cap theprocess time may be about, or is, 3 minutes.

FIGS. 18 g and 18 h show the change in the electro-spark depositionsurface coating of a sample after modification according to theultrasonic pressurized rotating friction process using this setup ofapparatus as described above.

In the example described, the microscopic views show an improvement inrespect of the coating defects. That is, the delaminations, cracks,discontinuities and voids are significantly reduced, or eliminated, withthe application of the process described. It is also noted that thegrain of copper alloy near the coating boundary zone has also beenrefined, i.e., made finer, after the process.

To summarise, the above example discloses a method and apparatus for theprocessing of a surface coating. It includes an ultrasonic pressurized,or force-biased, rotating friction head assembly that is used to applythe surface coating of the workpieces. The shape of the friction headcould either be flat or curved depending on the surface of the coatingon the workpiece. In this process, rotating action (i.e., rotation ofthe workpiece, or, more generally, relative motion between the workpieceand the coating apparatus to which the normal vector of contact isperpendicular) in conjunction with ultrasonic vibration while theapplicator is force-biased against the workpiece, is used to apply thesurface coating on the workpiece, and to improve the properties of thesurface coating. In the particular application, the apparatus used forthe ultrasonic pressurized rotating friction coating processing may havea work station in which to mount and in which to rotate a TiC coatedwelding electrode as the workpiece. There is an integrated rotatingfriction head assembly completed with an ultrasonic transducer; and anultrasonic power source. The process includes the integration of aforce-biased rotating friction device with an ultrasonic transducer. Theintegrated device, with the concurrent application of rotating frictionand ultrasonic vibration, may tend to reduce the defects that mightotherwise occur on the TiC coatings on welding electrodes produced usingthe electro-spark deposition process.

The process described, with the application of ultrasonic rotatingfriction under a normal force, may tend to improve the binding strengthof the ESD coating layers and also may tend to reduce or eliminatecoating defects. It may improve the physical and mechanical propertiesof the coating while preserving the material contents intact. Theapparatus and process of the example described may have advantages ofreduced cost and increased ease of use. In addition to treatingelectrospark deposition coating defects, this invention may also haveother applications, such as being employed to repair other surfacecoatings covering a wide range of applications. This description isintended to apply to such other coating applications as may be amenableto the application of the ultrasonic pressurized (or force-biased)rotating friction process.

Thus, in the forgoing, a welding electrode is mounted in a tool holderthat is part of a handle apparatus. The handle apparatus has anelectrode power connection. The handle apparatus has a housing defininga haft that can be grasped in the hand of an operator. A vibrator ismounted inside the haft. The vibrator includes a force transmitter inthe form of a cantilevered beam. The cantilevered beam is electricallyconductive and carries power to the tool holder. The tool holder has ahandle that permits the welding rod to be rotated about its axis as itwears during deposition of welding rod material on the object workpiece. The handle has a power supply that may vary voltage level topermit deposition cycles and peening cycles.

Description Pertaining to FIGS. 25 to 29

In the various Figures the annotations identify the following features:

-   -   A Electro-spark deposition ESD power source;    -   B Vibrating ESD coating applicator;    -   C Integrated transducer assembly I and workbench drive assembly        II;    -   D Ultrasonic Generator;    -   401 ESD power source positive terminal;    -   402 ESD power source negative terminal;    -   403 Resilient conductor spring;    -   404 Discharge electrode mounting;    -   405 Discharge electrode;    -   406 Eccentric wheel;    -   407 Handle;    -   408 Bakelite insulator;    -   409 Flexible shaft;    -   410 Low power applicator motor;    -   411 Workpiece;    -   412 Work bench negative terminal;    -   413 Integrated transducer negative terminal;    -   414 Integrated transducer positive terminal;    -   419 Integrated transducer body;    -   420 Transducer horn;    -   421 Ultrasonic transducer;    -   422 Flat pulley;    -   423 Ball bearing;    -   424 Jaw chuck;    -   425 Drill chuck;    -   II Drive assembly;    -   415 Work bench drive motor;    -   416 V-belt;    -   417 Ultrasonic power output negative terminal;    -   418 Ultrasonic power output positive terminal

The aspects of the invention to which FIGS. 18 g, 18 h, 25, 26, 27 a, 27b, 28 and 29 pertain may tend to provide a rotary electro-sparkdeposition surface coating process and apparatus, such as may beintended to improve electrode coating quality, tending to aid inincreasing electrode life. This invention is particularly suitable tothe application of electro-spark deposition coating of resistance spotwelding electrodes.

In an embodiment herein, a rotary electro-spark deposition surfacecoating process includes: mounting a workpiece on to a rotating base orfitting table. The surface of the workpiece is coated using anelectro-spark deposition (ESD) process. Ultrasonic vibration is appliedto the deposition layer during its crystallization phase. Thecrystallization phase of the deposition coating is completed whileultrasonic vibration continues to be applied to the workpiece. Theprocess is a rotary electro-spark deposition surface coating process. Inthis process the workpiece as described may be a resistance spot weldingelectrode.

In one embodiment, the rotary electro-spark deposition surface coatingapparatus may include: a vibrating ESD coating applicator, anelectro-spark deposition power source; an integrated transducerassembly; a drive or transmission at, or of, a table, or bench orwork-station for driving, e.g., rotating, the workpiece relative to thecoating applicator; and an ultrasonic vibration generator. The sonicvibration transducer may be mounted to co-operate with the work benchdrive. The workpiece is mounted to the integrated transducer and motivedrive assembly. In the process, the rotary electro-spark depositionsurface coating apparatus may coat or treat workpieces that may beresistance spot welding electrodes.

The rotary electro-spark deposition surface coating apparatus mayfurther include an electro-spark deposition power source A. Power sourceA may include an ESD power source positive terminal, 401, and an ESDpower source negative terminal, 402.

Vibrating applicator B (in essence, apparatus 20, 120, etc.) may includea spring conductor 3, a discharge electrode mounting screw 404, aconsumable welding rod of coating material, such as may be indicated asa discharge electrode 405, an eccentric wheel 406, a handle, or rodholder, or arm 407, a bakelite insulator 408, a flexible shaft 409 and alow power applicator motor 410.

In use integrated transducer assembly I may show, or have, the followingfeatures, namely a workpiece to be coated 411, work bench or workstationnegative terminal 412, an integrated transducer negative terminal 413,an integrated transducer positive terminal 414, an integrated transducerbody 419, a transducer horn 420, an ultrasonic transducer 421, a flatpulley 422, a ball bearing 423, a jaw chuck 424 and drill chuck 425.

Workbench drive assembly II may include, or have, a work bench orworkstation drive motor 415, and V-belt 416.

Ultrasonic generator D may have or include an ultrasonic power outputnegative terminal 417, and ultrasonic power output positive terminal418.

ESD power positive terminal 401 may be connected to a resilient memberidentified as a conductor spring 403. ESD power negative terminal 402 isconnected to workbench negative terminal 412. Discharge electrode 405 ismounted to the spring bar, namely conductor spring 403 by tightening adischarge electrode mounting screw 404. Applicator handle 407 isconnected to the low power motor 410 through a connection of, or with,flexible shaft 409. Eccentric wheel 406 is driven in rotation by thedriving of the low power motor 410 through the connection of flexibleshaft 409 and handle 407 for, or during, the vibrating coatingdeposition process.

Ultrasonic power output negative terminal 417 is connected to integratedtransducer negative terminal 413. Ultrasonic power output positiveterminal 418 is connected to integrated transducer negative terminal414. Integrated ultrasonic transducer assembly I is driven in rotationby drive motor 415 by the use of flat pulley 422 and V-belt 416.Ultrasonic vibration transducer 421 is connected to the integratedtransducer negative terminal 413 and integrated transducer positiveterminal 414, respectively. Transducer horn 420 and ultrasonictransducer 421 combine to act on the shaft of the rotary work platform.A tool holder, or seat, or mandrel, or center, or jig, in the form of adrill chuck 425, is mounted to the rotary work platform by means ofbeing clamped in the jaws of a rotatable driven chuck 424. Workpiece 411is mounted to drill chuck 425 during the rotary ultrasonic-assisted ESDprocess.

The vibrating applicator described above may act as the positiveterminal of the ESD process. It is connected to positive terminal, 401,of the ESD power supply. The discharge electrode 405 (i.e., the weldingrod composed of the coating material to be deposited on the workpiece)is mounted to conductor spring 403 by tightening discharge electrodemounting screw 404. Negative terminal 402 of the ESD power source, orpower supply, A, is connected the negative terminal 412 of the workbench or work station. Vibrating ESD deposition is carried out duringsimultaneous operation of the low power motor 410, flexible shaft 409,handle 408 and eccentric wheel 406.

The ultrasonic generator output positive terminal 418, and ultrasonicoutput negative terminal 417 are connected to the respective positiveand negative terminals 414 and 413 of the work bench respectively.

Transducer horn 420 is connected to the ultrasonic transducer 421 by ashaft. Transducer horn 420 then drives the jaw chuck 424 and the toolholder, namely drill chuck 425 of the work bench rotation through thecouplings of the rotating shaft. The ultrasonic transducer is containedinside a transducer casing or housing. The transducer casing is built ofinsulating materials. Jaw chuck 424 is mounted to the driven outputrotating shaft using a dedicated screw. Drill chuck 425 is then mountedto, or connected to, jaw chuck 424. The workpiece, in this embodimentresistance spot welding electrode 411, which is secured to or in drillchuck 425, is driven in rotation and the coating material is appliedaccording to the ultrasonic assisted electro-spark deposition process.The rotating shaft drive driven by motor 415 and the vibrating driveprovided by ultrasonic transducer 421 are thus, combined in anintegrated unit.

This description describes, inter alia, an apparatus such as may be usedto apply ESD coatings to work piece surfaces to modify the properties ofthose surfaces. The work pice may be moving, e.g., rotating during theprocess. That apparatus may be used according to an ESD coatingapplication procedure that may include the steps of:

1. Choosing a type of discharge electrode prepared with the propercomposition of materials for the desired ESD coating to be applied; andmounting the discharge electrode to the vibrating applicator. Aresistance spot welding electrode may be selected as the workpiece inthis application example.2. Turning on power to the apparatus, including power to theelectro-spark deposition power source, power to the ultrasonicgenerator, power to the workbench motor drive and to the vibratingapplicator. The process may include adjusting the associated operationalparameters including the vibrating applicator frequency, motor drivespeed and ultrasonic generator power. In the ultrasonic assistedelectro-spark deposition process, contact between the dischargeelectrode and the workpiece should be made lightly, with a component ofrelative horizontal (e.g., tangential) modulation movement to cause alayer of coating to be deposited on the workpiece surface. The timeduration of the process may depend on the thickness to be deposited andthe type of coating material. The basic principle is that the coating beapplied made evenly on the surface of the workpiece, and should coverthe surface completely. No base metal of the workpiece contact surfaceshould be left open or uncovered. Also, the time duration of theelectro-spark deposition process should not be too long, to avoidsoftening and annealing of the copper alloy material of the workpiece.3. Turning off the power to the workbench when the electro-sparkdeposition process is completed; and removing the coated electrode(workpiece) from the fixture assembly. This coating process may then berepeated with another uncoated workpiece, as may be.4. Turning off power to all other devices if there is another coatingprocess to implement.

The apparatus shown and described herein concerns use ofultrasonic-assisted ESD coating technology. It differs from traditionalvibrating ESD coating processes. Comparison may be made with patentCN102019531A:

1. In the apparatus and method described herein, ultrasonic vibration isapplied to the workpiece being coated in the electro-spark depositionprocess. Grain crystallization of the coating material takes place underthe application of ultrasonic vibration. By contrast, patentCN102019531A specifies the application of ultrasonic vibration to thedischarge electrode. The surface coating on the workpiece produceddirectly under the application of ultrasonic vibration is different fromthe ones produced by using the other approach. Having direct ultrasonicvibration applied to the workpiece is thought to be a new, useful, andunobvious feature of the apparatus and method shown and describedherein. Having ultrasonic vibration applied to the workpiece during thegrain crystallization of the coating material in the electro-sparkdeposition process is also understood to be a new, useful, and unobviousfeature shown and described herein. These features are thought to tendto improve grain refinement of the coating material and adhesion betweenthe coating and the metal matrix of the base substrate.2. In the apparatus shown and described herein, ultrasonic vibration isapplied to the workpiece being coated in the ESD process. Ultrasonicvibration in this case may improve or reduce the influence of theheat-affected zone (HAZ). Meanwhile the application of ultrasonicvibration to the discharge electrode as claimed in CN 10201931A appearsto have no influence on the HAZ between the ESD layer and the substratemetal matrix.

The apparatus and method described herein may have relative simplicityof operation, may be relatively low in cost, may have highapplicability, and may emit relatively little noise. In the embodimentor application example described herein, the ultrasonic power may be 70W, ultrasonic frequency may be 50 kHz, the rotational speed of theworkbench may be 700 rpm, the material of the discharge electrode may beTiC, the electro-spark deposition voltage may be 7V, and deposition timeduration may be 2 minutes.

For comparison, samples were produced with the same parameters exceptthat one set was treated with the application of ultrasonic vibration asdescribed herein, while the other sample was treated without ultrasonicvibration. From this comparison test, it was found that theelectro-spark deposition coating applied under ultrasonic vibrationexhibited improvements over the ones in which the coating was appliedwithout ultrasonic vibration: Higher coating hardness; reduction incoating defects; and better adhesion of the coating to the metal matrixsubstrate. Performing welding life tests, the working life of TiCelectro-spark deposition coated under ultrasonic vibration weldingelectrodes was found to be 800 welds while the ones coated withoutultrasonic vibration was 500 welds.

FIGS. 27 a and 27 b illustrate the microstructure of the coatingsproduced under the two different conditions. FIG. 27 b shows thatcoating defects are reduced when the coating is deposited at the sametime as ultrasonic vibration is applied to the workpiece. The size ofthe HAZ zone and its grain size is significantly less than that of thesample coated without the application of ultrasonic vibration as shownin FIG. 27 a.

FIG. 28 charts micro-hardness of coating layers applied with and withoutultrasonic vibration. It is observed that the micro-hardness of thecoating applied with the use of ultrasonic vibration (small round dotline) is very even across, such that a HAZ region transition is notobvious. Meanwhile it is noted that there is a section of themicro-hardness line of the coating applied without the use of ultrasonicvibration (small square dot line) has a significant drop in hardnessindicating the existence of the HAZ. It can be concluded that graingrowth in the HAZ at the coating is significantly affected by theapplication of ultrasonic vibration. The dendrites which exist in theHAZ area are reduced, or broken off, when the coating is produced withthe application of ultrasonic vibration on the workpiece. This may tendto avoid the formation of large grains and thus a significant HAZ.

FIG. 29 shows the microstructure of the coating applied according toPatent CN 102019531, in which ultrasonic vibration is applied to thedischarge electrode. In this case, ultrasonic power is 70 W, ultrasonicfrequency is 50 kHz, rotational speed of the work station is 700 rpm,the material of the discharge electrode is TiC, the electro-sparkdeposition voltage is 7V, deposition time is 2 minutes. By comparingFIGS. 29 and 27 a, the coating defects and the grain sizes of the HAZwhen coating with ultrasonic vibration applied to the dischargeelectrode appears to yield no significant difference from the coatingdeposited without application of ultrasonic vibration. A weldingelectrode life test was performed. It found that the welding life of theelectrode coated with the application of ultrasonic vibration to thedischarge electrode to be 500 welds. This is the same as the workinglife of the welding electrode coated without ultrasonic vibration.

With the ultrasonic-assisted electro-spark deposition technology, thisapparatus and method described herein may yield improved grainrefinement of the coatings, and may tend to avoid or reduce theoccurrence of a HAZ that might cause increased service problems. Theapparatus and method may tend effectively to overcome, or ameliorate,the defects and difficult problems of coatings produced usingconventional electro-spark deposition technology. In addition, the costof the apparatus may be modest, and the apparatus may be relativelysimple to operate. The apparatus and method described herein may have awide spectrum of application. Other than the resistance weldingelectrodes, the apparatus and method may be applied to the ESD coatingof other workpieces, such as rotating workpieces.

A surface modification process and apparatus for the electro-sparkdeposition (ESD) on a workpiece may include mounting a workpiece on arotationally driven mounting. The contact surface of the workpiece isESD coated. Ultrasonic vibration is applied to the deposition layerduring its crystallization phase. The workpiece may be a resistance spotwelding electrode. The apparatus may have a vibrating applicator, ESDpower supply, integrated ultrasonic transducer assembly, a work stationhaving a rotational drive and an ultrasonic generator. The ultrasonicgenerator is connected to the ultrasonic transducer. The ultrasonictransducer assembly and the rotating driving work bench unit areintegrated in a single assembly. The workpiece seats on the ultrasonictransducer assembly. The deposition of a surface coating occurs duringsimultaneous application of electro-spark deposition and ultrasonicvibration.

As explained above, in this third portion of the description there is amethod and apparatus for the processing of surface coating is disclosedconcerning the design of an ultrasonic pressurized rotating frictionhead assembly used to apply a surface coating to a workpiece. The shapeof the friction head may be flat or curved as appropriate for theworkpiece. The surface coating is rotated under repeated contact andultrasonic vibration. The apparatus includes: a work station for themounting and rotation of a TiC coated welding electrode workpiece; arotating friction head assembly with an ultrasonic transducer and powersource. Concurrent application of pressurized rotating friction andultrasonic vibration, may tend to reduce the defects in the TiC coatingson welding electrodes produced using the electro-spark depositionprocess. While maintaining the basic coating material componentcontents, mechanical and physical properties unaltered, defects such asdelaminations, cracks, discontinuities and voids may be reduced. Controland operation of the may be adapted to other applications.

In FIG. 19 there is a welding arrangement. In that arrangement there isa workpiece 440, which may be a single workpiece, or may be twoworkpieces 442, 444 that are to be joined together. In some instances abacking bar 446 may be provided to prevent weld-through of work pieces442, 446 at the penetration at, for example, a bevel weld 448. The depthof the bevel, and the depth of the abutting edges of items 442 and 444below the bevel may depend on the expected depth of penetration of theweld.

Although the workpiece is shown in two parts in the context of weldingthe two parts together, workpiece 440 could be a single workpiece, andthe bevel may be a slot, or groove or channel, or gouge. That is, insome embodiments, the process may be filling a gouge or damage ofwhatever cause where the gouge needs to be filled. In other embodiments,the accommodation in the surface may be a slot or groove that forms theroot or base of a dissimilar material insert, such as may be desired toadd a ceramic insert for a wear surface or cutting element, such as in adrill bit or in forestry equipment, or in mounting teeth or wearsurfaces on mining or construction equipment, such as the teeth ofloaders, buckets, and so on.

However it may be, a welding tool, or welding head, or welder, orwelding electrode, is shown generally as 450. It may include anelectrode holder 452 and may have mounted therein an electrode 454. Theelectrode may be a consumable electrode rod 456. Holder 452 may be avibrating holder, and may be a vibrating holder as describedhereinabove, such as items 20 and 120, or as may be. Holder 452 may behand-held, or may be mounted to a welding head or frame or jig, orwelding table, such as suggested by the arrangement of FIG. 20, forexample. However it may be, holder 452 may be a vibrating holder, andmay be provided with a power supply as described above such as may beoperable at a first voltage, such as an initiation or striking voltage,and at a second, lesser voltage. That lesser voltage may be zero.Whatever the lesser voltage may be, during the cycles of vibration ofholder 452 (and therefore of rod 456) in which the lesser voltage isapplied, the electrode may agitate the deposited material 458, and wherethat material has begun to solidify, to strike that material in thehitting, deforming, or peening manner discussed above.

Whatever the case may be, the workpiece is secured appropriately to thejig or table, or holder, or mounting, or fixture (however it may betermed) for the welding process, whether by clamping or other means. Theworkpiece may be secured to a movable bed. The movable bed may have asingle degree of freedom of motion (as in being spun or rotated in asingle angular degree of freedom; or as in linear translation in atranslational degree of freedom); or it may have more than one degree offreedom of motion, whether those degrees of freedom include, forexample, x and y translation, or also include an angular degree offreedom, alpha or theta. The motion may be reciprocating motion. Themotion may also follow a particular path, such as a programmed path,such as may follow a line or contour or pattern (e.g., to follow a weldfillet, or the shape of a gouge or other damage, or a desired wear plateor insert, boundary, shape or pattern, as may be.

Alternatively, or additionally, or equivalently, the workpiece may beheld on a stationary bed or fixture while holder 452 may be movable, orboth the bed and holder 452 may have degrees of freedom of motion suchthat they can move relative to each other.

Whether or not a backing bar is used, once an initial pass has been laiddown, the weld may be self-backing. That is, an initial weld may be madein the normal manner, with or without vibration of holder 452.Subsequent passes may follow, with holder 452 set to vibrate. Severalpasses may be applied to build up a weldment.

Also in the arrangement of FIG. 19, a vibration transmission isindicated as 460. There may be a single vibration head 462, or more thanone head, 464, 466, 468. At least one of the heads is actively operableto transmit vibration to the workpiece. One or more of the other headsmay act as stationary reaction members, or abutments, or all of them maybe “live”. They may transmit on individual frequencies. The frequenciesneed not be the same. They may be the same frequencies, or ranges offrequencies as described above. Some of the heads may be on one side ofthe material, some may be on the other side of the weldment in they-direction, or, alternatively, or additionally, may be on oppositefaces of the workpiece, as shown. Pairs of heads may be opposed, such as462, 466, or 464, 468.

It may be that one or more of the heads has an engagement member, orpad, or sole plate, or foot 470. It may be that foot 470 is free ofgouging or plastic deformation elements. That is, whereas indenters orother probes for vibrating workpieces are known, the act of indentingmay introduce local plastic deformation defects or non-homogeneities, orsingularities in the workpiece where such defects may not be desired,e.g., as where they may tend subsequently to act as fatigue initiationsites. Foot 470 may therefore not include, that is, may be free of,plastic deformation members, such as indentation members. Foot 470 maybe substantially flat or smooth. In some embodiments, foot 470 may be aroller, whether cylindrical or spherical. In either case foot 470provides a workpiece engagement, or workpiece interface, member, thatacts as a vibration transmitter or transmission member or transitioninterface, through which an exciting vibration may be introduced intothe adjacent workpiece. Foot 470 may be clamped or otherwise heldagainst the workpiece. Foot 470 may be urged against the workpiece withbiasing members, such as springs, which are themselves backed by a jog,or fitting, or frame.

The vibration so introduced into the workpiece may be ultrasonicvibration, such as described above. The vibration need not besinusoidal, and need not be period. It may, however, be convenient forthe vibration to have a given frequency (which may be adjustable) andamplitude. The vibration imposed upon the workpiece may be independentof the vibration applied to holder 454, and may be applied whetherholder 454 is then vibrating or not. Vibration may be applied to theworkpiece when holder 454 is not transmitting welding current to theworkpiece, or when the welding current is at the reduced voltage. Thevibration imposed on the workpiece may be imposed either during thewelding material deposition, or during agitation or peening at reduced(or zero) voltage.

As suggested in FIG. 20, the welding head (which may be multiple weldingheads) may be mounted on a frame 470. And the workpiece may be mountedon a moving table or bed 472, suggested by an array of rollers 474. Thetable or bed may, for example, move in translation under electrode 474,such as horizontally in the x-direction (across the page as shown) ortransversely in the y-direction (into or out of the page as shown).These degrees of freedom of motion may be independent of any vibratoryor oscillatory drive. That is, ultrasonic vibration may take place at avery small scale of displacement. The table or bed may move globally.The table or bed or welding head may be programmed to follow a pathwhich one or the other, or both, of the welding head and the workpiecevibration exciter is in operation.

The various materials, processes, drives, voltages and frequencies ofthe embodiments described above in the context of FIGS. 1 to 17 and 21to 29 are applicable to the apparatus and method pertaining to FIGS. 19and 20. The welding tool of the apparatus and method of FIGS. 21-29 maybe the apparatus of FIGS. 1-17, suitably adjusted and employed toconform to that description.

As many variations and modifications are possible, the application ofthis invention covers is intended not only to encompass the abovementioned example, but also to encompass such other concepts oralternations falling within the principles, aspects, and features of theinvention shown and described herein.

What has been described above has been intended illustrative andnon-limiting and it will be understood by persons skilled in the artthat other combinations of the features described above, andmodifications, may be made without departing from the scope of thedisclosure as defined in the claims appended hereto. Various embodimentsof the invention have been described in detail. Since changes in and oradditions to the above-described apparatus and process may be madewithout departing from those aspects, the invention is not to be limitedto those details but only by the appended claims

We claim:
 1. A welding apparatus comprising: a fixture to which tosecure at least one workpiece; a welding head positioned to address aworkpiece held in the fixture; said fixture having a vibration source bywhich to transmit vibration to the workpiece; and said welding headbeing one at least of (a) operable during welding to vary voltagebetween a first magnitude and a second magnitude; and (b) operableduring welding to vibrate independently of said fixture.
 2. The weldingapparatus of claim 1 wherein said apparatus includes at least oneultrasonic vibration head operable to transmit ultrasonic vibration tothe workpiece during welding.
 3. The welding apparatus of claim 1wherein said apparatus includes a power source operable to drive saidwelding head in a welding mode and in a peening mode.
 4. The weldingapparatus of claim 1 wherein at least one of said fixture and saidwelding head includes a motion transmitting drive apart from a vibrationdrive, said motion transmitting drive being operable globally to causerelative motion between the fixture and the welding head.
 5. The weldingapparatus of claim 5 wherein at least one of said fixture and saidwelding head is programmable to move according to a pre-set course. 6.The welding apparatus of claim 1 wherein, in use, the welding head isbiased against the workpiece.
 7. The welding apparatus of claim 1wherein the vibration source of the fixture has an engagement member forcontacting the workpiece, and said engagement member is free fromplastic deformation elements.
 8. The welding apparatus of claim 1wherein said welding apparatus is both (a) operable during welding tovary voltage between a first magnitude and a second magnitude; and (b)operable during welding to vibrate independently of said fixture.
 9. Amethod of welding a workpiece, said method comprising: mounting avibration source to transmit a first vibration signal to the workpiece;opposing the workpiece with a welder; operating the welder according toat least one of: (a) operating at a first voltage magnitude for a firsttime period; and operating at a second voltage magnitude at a secondtime period; and (b) vibrating the welder according to a secondvibration signal; and operating the vibration source while operating thewelder.
 10. The method of claim 9 wherein said method includes vibratingthe welder to peen deposited weld metal during transmission of the firstvibration signal.
 11. The method of claim 9 wherein the second voltagemagnitude is zero.
 12. The method of claim 9 wherein said methodincludes securing the workpiece in a fixture.
 13. The method of claim 12wherein said method includes moving at least one of the fixture and thewelding head along a pre-programmed path while transmitting said firstvibration signal to the workpiece.
 14. The method of claim 9 wherein theworkpiece has more than one part, and said method includes welding atleast two parts of the workpiece together.
 15. The method of claim 9wherein the method includes operating the welder to deposit a materialon the workpiece that is different from the parent material of theworkpiece.
 16. The method of claim 9 wherein said method is a method ofsurface coating the workpiece.
 17. The method of claim 9 wherein thefirst vibration signal is an ultrasonic vibration signal said methodincludes both (a) operating at a first voltage magnitude for a firsttime period; and operating at a second voltage magnitude at a secondtime period; and (b) vibrating the welder according to a secondvibration signal; and operating the vibration source while operating thewelder.
 18. The welding process of claim 9 wherein ultrasonic vibrationis applied directly to the workpiece during at least one of: (a)application of a welding rod to the workpiece; (b) crystallization ofwelded material; and (c) peening of welded material.
 19. The weldingprocess of claim 18 wherein ultrasonic vibration is applied to theworkpiece during at least two of: (a) application of a welding rod tothe workpiece; (b) crystallization of welded material; and (c) peeningof welded material.
 20. The welding process of claim 19 wherein saidwelding process is an ESD process and the welder uses a welding rodhaving a ceramic material composition that includes at least one of (a)TiC; and (b) TiB₂.